Which Hydration Serum Reigns Supreme?

Authors: Alyssa Palazzo, Justina Szczypinski, Mikayla Celli, Webster Magcalas
Reading Time: 38 minutes
Level: Intermediate

 

Purpose: The main purpose of this study was to assess the hydration ability of 11 cult favorite hydration serums. We also aimed to assess the correlation between subjective hydration feel and empirically measured hydration. 

Disclaimer: The following results are from a “Quick Study” - done out of scientific curiosity by our R&D team, essentially a fun internal experiment.

While it was carefully conducted using lab-grade measurement equipment, the study design is far from perfect and there are many limitations we'll discuss throughout.

To underscore the fun and scientific spirit of this experiment, we’re only publishing the product ingredient (INCI) lists here, and we did not include our own hydration serum.

What is a hydration serum?

Moisturizing or hydrating serums are essential components in a basic skincare regimen. They protect the skin from dehydration which can be the root of more serious skin problems. Hydration serums are typically formulated with high concentrations of humectants, which are a class of ingredients that function to increase hydration in the skin. Read more about humectants here.

What to look for when selecting a hydration serum: 

• Multiple high-concentration humectants - humectants have different means of increasing hydration in the skin. Having multiple humectants ensure that the product is comprehensively addressing  hydration. One easy rule of thumb is to choose products where the first five ingredients are packed with powerful hydrators.
• Skin compatible humectants - your skin naturally contains humectants called Natural Moisturizing Factors (NMF), responsible for giving your skin its plump and hydrated appearance. These very same humectants are some of the best available skincare ingredients. Look for: glycerin, panthenol (vitamin B5), hyaluronic acid, sodium PCA, urea, lactic acid, and amino acids. 
• Semi-occlusives - these ingredients, like polysaccharides and silicone, help retain that extra moisture brought by humectants. 
• Low pH - don’t forget about the pH. We want serums to be skin compatible as much as we can. If they need to be out of range, it’s not the end of the world. Learn more about layering with pH here. 

Procedure 

In order to reduce the presence of bias as much as possible, it was essential to make this a blinded study. This was essential in the subjective portion of this study to ensure participants didn’t just advocate for their favourite serum or one with a high price tag. The participants (n=6 - yes, we know) were unaware of the identity of the products as each was removed from their original packaging and placed into identical, randomly numbered bottles. No other identifying information was shared with the participants (e.g., brand, price point).

The study included both a subjective and objective evaluation. For the subjective evaluation, participants rated each serum on a scale of 1-10 as they applied the product to the skin. Here they focused on texture, skin-feel, and most importantly, how hydrating each product felt. Next, the participants were asked to look at the ingredient list (INCI) for each product and rate, on a scale of 1-10, how well they thought each product would perform.

The objective portion of the study was designed to evaluate the effect the serums had on the hydration levels in the skin as accurately as our Quick Study would allow. The instrument that we used to measure skin hydration was a Corneometer, which is an extremely sensitive piece of equipment used to measure the level of hydration. It works by measuring the capacitance of the stratum corneum, which is the standard method of assessing skin surface hydration. The measurement depth of this instrument (10-20 μm of the stratum corneum) is calibrated to so that there is no influence from deeper skin layers (e.g., from the blood vessels), in order to obtain a highly accurate measurement of moisture in the skin.

Baseline measurements were taken for each participant to assess the initial hydration level of their skin. Measurements were taken 2 hours after application following the Corneometer standard operating procedure and following the methodology of previous studies. The serums were applied to the forearms in pre-designated areas, and a similar amount was applied for each serum by all participants. Following the 2 hours, hydration measurements were taken on each area to be compared with the baseline value for each participant. The change in hydration was obtained by subtracting the test measurements from the negative control. These values were then normalized and analyzed using ANOVA and posthoc tests.

 

Subjective Results 

The subjective scores were collected from all participants, and the values for each serum were averaged:

Serum #	Average Score	Comments
1	6.8	3 out of 6 said it gives the skin a soft feel  Commonly described as “creamy”
2	7.8	Almost all participants mentioned a soft skin-feel 4 out of 6 agreed this formula felt "too watery"
3	7.2	2 out of 6 agreed it was "too sticky"  Left a white cast on 1 participant
4	7.4	A number of comments regarding good spreadability and thick consistency
5	7.4	5 out of 6 described this serum as “very hydrating”
6	5.4	Described as a watery consistency 2 out of 5 stated it dried very quickly
7	6.4	Many comments regarding difficulty absorbing into the skin
8	6.2	Mentions of good absorption and spread
9	7.8	3 out of 6 felt it was “very hydrating”
10	7.6	Described to have a thicker consistency and good absorption 2 out of 6 felt it was too sticky
11	6.4	Watery texture 4 out of 6 mentioned it had difficulty absorbing and stayed on top of the skin

 

As can be seen, the values did not show a huge degree of variance between how participants rated the subjective feel of the 11 serums. Participants had varying opinions on their ideal texture for serum and what properties lead to a more hydrating feel. Serums 2, 9 and ranked particularly high (7.8 vs an average of 6.9). Participants felt these left their skin feeling most hydrated and had the most appealing texture.

Serum 6 was the distinct low scorer of the panel's subjective perceptions (5.4 vs an average of 6.9) - more to come on this point below!

 

INCI Results + pH measurement

Serum Number	pH measurement
1	6.0-6.5
2	4.5-5.0
3	6.5-7.0
4	5.0-5.5
5	6.0-6.5
6	5.0-5.5
7	6.5-7.0
8	4.5-5.0
9	4.0-4.5
10	4.5-5.0
11	6.5-7.0

 

Product breakdown and discussion summary

Serum # 1

Inci: Aqua/Water/Eau, Glycerin, Cetearyl Ethylhexanoate, Dimethicone, Ammonium Polyacryloyldimethyl Taurate, Sodium Hyaluronate, Panthenol, Ceramide Np, Ceramide Ap, Ceramide Eop, Carbomer, Cetearyl Alcohol, Behentrimonium Methosulfate, Sodium Hydroxide, Sodium Lauroyl Lactylate, Cholesterol, Phenoxyethanol, Disodium Edta, Isopropyl Myristate, Caprylyl Glycol, Citric Acid, Xanthan Gum, Phytosphingosine, Ethylhexylglycerin.

• Glycerin: One of the best humectants but a little sticky
• Cetearyl Ethylhexanoate: Manufacturer notes: “LANOL™ 1688 is an emollient oil which is distinguished by excellent application on the skin, fast absorption into the skin, a soft non-greasy, non-sticky feel, very easy emulsification and a good resistance to oxidation.” 
• Dimethicone: Silicone
• Ammonium Polyacryloyldimethyl Taurate: Polymeric emulsifier
• Sodium Hyaluronate: a salt form of Hyaluronic acid
• Panthenol: aka Pro-Vitamin B5, good humectant and barrier repair agent
• Ceramide Np, Ceramide Ap, Ceramide Eop, Carbomer, Sodium Lauroyl Lactylate, Cholesterol, Xanthan Gum, Phytosphingosine: Manufacturer Notes: “SK-influx® is a skin-identical lipid concentrate for enhanced skin moisturization and protection.” This is a ceramide complex. 
• Cetearyl Alcohol, Behentrimonium Methosulfate: BTMS-25 cationic emulsifier that acts as a skin/hair conditioner
• Sodium Hydroxide, Citric acid: pH adjusters
• Disodium Edta: a chelating agent
• Isopropyl Myristate: dry emollient for a quick evaporation-feel
• Phenoxyethanol, Caprylyl Glycol, Ethylhexylglycerin: preservatives

Skin Science Discussion Notes:

• "This looks like a great light moisturizer. It has good humectants like Glycerin, Sodium Hyaluronate and Panthenol combined with possible occlusive in Dimethicone."
• "Bonus is the added Ceramide complex."
• "It has a pH of 6.0-6.5, which is on the higher side, so it’s not a good product ender in terms of pH." 

Formulation Discussion Summary: This is a simple ceramide complex light moisturizer. I’m sure we’ve hammered down our point that SK-influx (Ceramide Complex) has about 1.5% of total Ceramides. So if you use it at 5% in the total formulation, you get 0.075% of total Ceramides. Of course, we can’t really know the exact percentage of ingredients they used, but we have a general idea of how much Ceramides are in it. This Ceramide Complex destabilizes emulsions because of the effect of the barrier lipids. They’re using BTMS-25 + a polymeric emulsifier (poss. Aristoflex AVC), and we’ve tested this particular combination, and you can’t add more than 5% of Ceramide Complex in it. A better way is to do an LC-MS measurement of ceramides. 

Average Blind INCI Score: 5.75/10 

Serum #2

Inci: Water, Butylene Glycol, Dimethyl Sulfone, Betaine, Caprylic/Capric Triglyceride, Natto Gum, Sodium Hyaluronate, Disodium Edta, Centella Asiatica Extract, Glycyrrhiza Glabra (Licorice) Root Extract, Polyquaternium-51, Chlorphenesin, Tocopheryl Acetate, Carbomer, Panthenol, Arginine, Luffa Cylindrica Fruit/Leaf/Stem Extract, Beta-Glucan, Althaea Rosea Flower Extract, Aloe Barbadensis Leaf Extract, Hydroxyethylcellulose, Portulaca Oleracea Extract, Lysine Hcl, Proline, Sodium Ascorbyl Phosphate, Acetyl Methionine, Theanine, Lavandula Angustifolia (Lavender) Oil, Eucalyptus Globulus Leaf Oil, Pelargonium Graveolens Flower Oil, Citrus Limon (Lemon) Peel Oil, Citrus Aurantium Dulcis (Orange) Peel Oil, Cananga Odorata Flower Oil, Copper Tripeptide-1

• Butylene Glycol: multipurpose glycol that functions as a humectant, antimicrobial, and emollient
• Dimethyl Sulfone: a potential anti-inflammatory, antioxidant, anti-pigment active
• Betaine: an osmolyte and a humectant
• Caprylic/Capric Triglyceride: an emollient
• Disodium Edta: a chelating agent
• Natto Gum: humectant, film former
• Sodium Hyaluronate: a salt form of Hyaluronic acid
• Centella Asiatica Extract: source of pentacyclic triterpenes that can be used for hydration, anti-inflammatory and anti-aging
• Glycyrrhiza Glabra (Licorice) Root Extract: source of anti-inflammatory agents like Glycyrrhetinic acid
• Polyquaternium-51: a conditioning agent and a film former to reduce water loss
• Tocopheryl Acetate: a form of Vitamin E, antioxidant
• Carbomer: thickening/ gelling agent
• Panthenol: aka pro-Vitamin B5, good humectant and barrier repair agent
• Arginine, Lysine Hcl, Proline, Acetyl Methionine, Theanine:  amino acids function as humectants
• Luffa Cylindrica Fruit/Leaf/Stem Extract: (Hetima extract J) this is a type of hemicellulose polymer that forms a film to increase hydration and reduce water loss
• Beta-Glucan: hydrating and anti-aging active derived from oats or yeast
• Althaea Rosea Flower Extract: another extract that functions as a texture enhancer
• Aloe Barbadensis Leaf Extract: aloe vera extract, hydrating, soothing
• Hydroxyethylcellulose: thickener
• Portulaca Oleracea Extract: from purslane, soothing agent apparently
• Sodium Ascorbyl Phosphate: antioxidant, a form of Ascorbic acid
• Lavandula Angustifolia (Lavender) Oil, Eucalyptus Globulus Leaf Oil, Pelargonium Graveolens Flower Oil, Citrus Limon (Lemon) Peel Oil, Citrus Aurantium Dulcis (Orange) Peel Oil, Cananga Odorata Flower Oil: a bunch of essential or fragrance oils
• Copper Tripeptide-1: a peptide. Possible anti-aging effects
• Chlorphenesin: preservative

Skin Science Discussion Notes:

• "The main solvent here is Butylene Glycol, which has a bad rep for acne, but it is one of the most hydrating glycols."
• "It also has Dimethyl Sulfone (MSM), which is popular in alternative medicine for anti-inflammatory. I think it is used here as that as well."
• "Betaine is a fascinating ingredient as it acts as a soothing agent not only in skincare but also in toothpaste."
• "Natto gum is another exciting ingredient as it contains gamma-Polyglutamic acid (PGA). As the name suggests, PGA is composed of long chains of the amino acid Glutamic acid, which is capable of binding water. You end up having a long chain of sponges that are soaked with water. It is quite popular in Korean skincare as it stays on the skin’s surface for that glassy, hydrated look."
• "I’m not a fan of extracts because we don’t know their composition, but Centella Asiatica and Licorice are among our favourite botanicals. Centella asiatica produces pentacyclic triterpenes that have shown promise in hydration, anti-inflammatory and wound repair. Licorice, on the other hand, is the source for Glycyrrhetinic acid which is a potent anti-inflammatory agent."
• "The serum has a dash of anti-aging, antioxidant but I think these are mostly fluff. It has a pH of 4.5-5.0, which is absolutely perfect; those amino acids can also act as buffers that can resist pH changes in the skin."

Formulation Discussion Summary: Butylene Glycol mixed with solubilized Capric/Caprylic Triglycerides carry the majority of the solution. I think what makes this unique is the presence of various film formers. You have Natto Gum, Sodium Hyaluronate, Polyquats, Luffa Cylindrica Fruit/Leaf/Stem Extract etc. Because most of these are polymers capable of holding water, they form a water-holding film on top of your skin. This is a great technique to achieve that glassy skin. A word of caution, this seems to be a Korean product, so they have a slightly different regulation in listing INCI, so we can’t compare them directly with North American INCI. 

Average Blind INCI Score: 6.25/10.

 

Serum #3

INCI Aqua (Water), Sodium Hyaluronate, Pentylene Glycol, Propanediol, Sodium Hyaluronate Crosspolymer, Panthenol, Ahnfeltia Concinna Extract, Glycerin, Trisodium Ethylenediamine Disuccinate, Citric Acid, Isoceteth-20, Ethoxydiglycol, Ethylhexylglycerin, Hexylene Glycol, 1,2-Hexanediol, Phenoxyethanol, Caprylyl Glycol.

• Sodium Hyaluronate: a salt form of Hyaluronic acid
• Pentylene Glycol: a glycol that acts as a humectant and a preservative
• Propanediol: a multifunctional glycol that acts as a solvent and a humectant
• Sodium Hyaluronate Crosspolymer: a more cross-linked Hyaluronic acid. Improves the texture of the solution
• Panthenol: aka pro-Vitamin B5, good humectant and barrier repair agent
• Ahnfeltia Concinna Extract: Red Marine Algae, has polysaccharides, so it helps prevent water loss on the surface
• Glycerin: an excellent humectant, a bit sticky
• Trisodium Ethylenediamine Disuccinate: a chelating agent
• Citric acid: pH adjuster
• Isoceteth-20: a solubilizer to keep oils dissolved in the solution
• Ethoxydiglycol: a penetration enhancer but also used as an emollient for a dry finish
• Ethylhexylglycerin, Hexylene Glycol, 1,2-Hexanediol, Phenoxyethanol, Caprylyl Glycol:  preservatives

Skin Science Discussion Notes:

• "This has two forms of Hyaluronic acid: Sodium Hyaluronate and Sodium Hyaluronate Crosspolymer. The usual Molecular Weight for Sodium Hyaluronate is around 1M Daltons. For Sodium Hyaluronate Crosspolymer, it’s Millions of Daltons that are cross-linked together, ending up with an unlimited Dalton size."
• "Again, we see another extract here that contains polysaccharides from Red Marine Algae. Like any water-absorbing polymer, it sits on the surface of the skin and prevents water from evaporating."
• "Okay, so we now know several polymers that we call semi-occlusives. They aren’t really occlusives, but they slow down water loss by holding on to moisture in the top layer of the skin. They all act similar to each other:
• Sodium Hyaluronate
• Sodium Hyaluronate Crosspolymer
• gamma-Polyglutamic acid from Natto gum
• Polyquats
• Extracts with Polysaccharides (Luffa, Ahnfeltia Concinna, etc.)
• "this one has a pH of 6.5-7.0, which is pretty high. I’m looking at the INCI, and there is no reason for it to be this high. If you are using this, you definitely want to bring down your pH afterward with another product. The good thing is, it doesn’t have a lot of buffering agents, so bringing down the pH should be okay."

Formulation Discussion Summary: This is a pretty simple hydration serum with humectant and semi-occlusives. Notice the humectant choice for the first five ingredients. Panthenol and Glycerin aren’t in the top 5 because they are pretty sticky. I think the texture was an important factor in the formulation. This is echoed with the use of Ethoxydiglycol (EDG). EDG is a solvent and a penetration enhancer, but it also imparts a powdery dry feel to the solution. 

Average Blind INCI Score: 7.25/10

 

Serum #4

INCI: Aqua / Water / Eau, Cyclohexasiloxane, Glycerin, Alcohol Denat., Hydroxypropyl Tetrahydropyrantriol, Propylene Glycol, Dipotassium Glycyrrhizate, Polysilicone-11, Polymethylsilsesquioxane, Sodium Hyaluronate, Dimethicone, Tocopherol, Phenoxyethanol, Capryloyl Salicylic Acid, Octyldodecanol, Bis-Peg/Ppg-16/16 Peg/Ppg-16/16 Dimethicone, Peg-20 Methyl Glucose Sesquistearate, Ammonium Polyacryloyldimethyl Taurate, Caprylyl Glycol, Xanthan Gum, Dextrin, Oryza Sativa Extract / Rice Extract, Disodium Edta, Caprylic/Capric Triglyceride, Sodium Hydroxide, Adenosine, Citrus Nobilis Peel Oil / Mandarin Orange Peel Oil, Limonene, T-Butyl Alcohol, Cellulose Acetate Butyrate, Polyphosphorylcholine Glycol Acrylate, Polyvinyl Alcohol, Sodium Chloride, Butylene Glycol, Pentaerythrityl Tetra-Di-T-Butyl Hydroxyhydrocinnamate

• Cyclohexasiloxane: a silicone
• Glycerin: a great humectant
• Alcohol Denat.: solvent or to achieve a drier finish
• Hydroxypropyl Tetrahydropyrantriol: Pro-xylane, potential anti-aging active
• Propylene Glycol: a glycol that functions as a humectant and potentially decreases water loss
• Dipotassium Glycyrrhizate: a water-soluble form of Glycyrrhetinic acid from Licorice, anti-inflammatory, 
• Polysilicone-11, Polymethylsilsesquioxane: silicone elastomer, texture enhancer for a powdery after-feel
• Sodium Hyaluronate: a salt form of Hyaluronic acid
• Dimethicone: a silicone emollient
• Tocopherol: antioxidant
• Phenoxyethanol, Caprylyl Glycol: preservatives
• Capryloyl Salicylic Acid: a more lipophilic Salicylic acid, potential anti-inflammatory and exfoliant
• Octyldodecanol: a medium spreading emollient
• Bis-Peg/Ppg-16/16 Peg/Ppg-16/16 Dimethicone, Caprylic/Capric Triglyceride: a silicone-based emulsifier
• Peg-20 Methyl Glucose Sesquistearate: an emulsifier
• Ammonium Polyacryloyldimethyl Taurate: a thickener
• Xanthan Gum: also a thickener
• Oryza Sativa Extract / Rice Extract, Dextrin: an extract with some antioxidant ability
• Disodium Edta: a chelating agent
• Sodium Hydroxide: pH adjuster
• Adenosine: a nucleoside, anti-aging?
• Citrus Nobilis Peel Oil / Mandarin Orange Peel Oil, Limonene: fragrance oil
• T-Butyl Alcohol, Cellulose Acetate Butyrate, Polyphosphorylcholine Glycol Acrylate, Polyvinyl Alcohol: plasticizer, viscosity control
• Sodium Chloride: viscosity control
• Butylene Glycol: emollient, solvent
• Pentaerythrityl Tetra-Di-T-Butyl Hydroxyhydrocinnamate: antioxidant, stabilizer

Skin Science Discussion Notes: There’s not a lot of humectants in this one but it doesn’t mean that it is not hydrating. The only major ones are Glycerin and Sodium Hyaluronate. It could be that they are in higher concentrations that’s why they had to use denatured alcohol and silicones to counteract the tackiness. It has a pH of 5.0-5.5 which is great, no adjustments needed. 

Formulation Discussion Summary: This is a different way of hydrating the skin. In previous hydration serums, we saw lots of humectants that can replace water. The reason we apply those kinds of humectants is that they have a lower vapour pressure than water, so they evaporate less than water. In this formulation, it hydrates the skin by not allowing water to escape. It has several silicone elastomers, and some of them are good at reducing TEWL. You see some of these ingredients in luxurious creams and serums where you are aiming for a water-break sensation upon contact with skin, but then it magically turns powdery at the finish. You can only get that with silicone elastomers. Just by looking at the INCI, I can guess that this serum would be one of the top serums that are subjectively hydrating. Skincare texture is very personal and how serums break on our skin can evoke certain emotions which may trick our brain into thinking that it is very hydrating. 

Average Blind INCI Score: 6/10

 

Serum #5

INCI: Water, Coconut Alkanes, Ammonium Acryloyldimethyltaurate/Vp Copolymer, Glycerin, Pentylene Glycol, Sclerocarya Birrea Seed Oil, Wheat Amino Acids, Ananas Sativus (Pineapple) Fruit Extract, Berberis Vulgaris Root Extract, Citrullus Lanatus (Watermelon) Fruit Extract, Lens Esculenta (Lentil) Fruit Extract, Pyrus Malus (Apple) Fruit Extract, Coco-Caprylate/Caprate, Panthenol, Sodium Pca, Sodium Hyaluronate Crosspolymer, Dipotassium Glycyrrhizate, Niacinamide, Cyclodextrin, Sodium Hyaluronate, Sodium Lactate, Phenoxyethanol, Hydroxyproline, Trisodium Ethylenediamine Disuccinate, Citric Acid, Caprylyl Glycol, Chlorphenesin, Ethylhexylglycerin.

• Coconut Alkanes, Coco-Caprylate/Caprate: silicone replacements, emollients
• Ammonium Acryloyldimethyltaurate/Vp Copolymer: polymeric emulsifier
• Glycerin: an excellent humectant
• Pentylene Glycol: a multifunctional glycol, humectant, preservative
• Sclerocarya Birrea Seed Oil: a silicone replacement, emollient
• Wheat amino acids: humectant
• Pineapple, Watermelon, Lentil, Apple extract: the worst fruit salad only my drunk uncle would bring for Thanksgiving. Perhaps hydration and exfoliation?
• Panthenol: pro-Vitamin B5, humectant, good barrier-repair active
• Sodium PCA: an NMF, humectant
• Sodium Hyaluronate Crosspolymer: HA with more cross-linking. Imparts a luxurious feel to the serum
• Dipotassium Glycyrrhizate: a water-soluble form of Glycyrrhetinic acid, anti-inflammatory
• Niacinamide: hydrating, anti-acne active
• Cyclodextrin: this is probably mixed in one of the actives above. It is used for delivering substances to the skin
• Sodium Hyaluronate: salt version of HA
• Sodium Lactate: another NMF
• Phenoxyethanol, Caprylyl Glycol, Chlorphenesin, Ethylhexylglycerin: preservative
• Hydroxyproline: primary amino acid in collagen
• Trisodium Ethylenediamine Disuccinate: chelating agent
• Citric acid: pH-adjuster

Skin Science Discussion Notes:

• "This one has good humectants like glycerin, hyaluronic acid, panthenol, sodium PCA, HA Crosspolymer, sodium lactate, coupled with good actives like Dipotassium Glycyrrhizate and Niacinamide."
• "We can’t really know what’s in the fruit salad extract, but they can at least be hydrating because of the glycol solvent they have."
• "This has a pH of 6.0-6.5, which is a bit high, but it should be fine if you are using a product with a lower pH afterward."

Formulation POV: This is a natural formulation, and there’s nothing wrong with that. They used silicone alternatives like Coconut Alkanes and Coco-Caprylate/Caprate. Some people avoid silicones because their skin doesn’t sit well with silicones, and some people also react to Coconut Alkanes. I think the lesson here is that do whatever floats your boat. Even alcohol can have a place in a formulation. Some actives are only soluble in alcohol, and they can also put lots of humectants and barrier lipids to counteract the drying effects of alcohol. 

Average Blind INCI Score: 6.75/10

Serum #6

INCI: Water (Eau), Glycerin, Butylene Glycol, Panthenol, Pentylene Glycol, Phenoxyethanol, Acrylates/C10-30 Alkyl Acrylate Crosspolymer, Trehalose, Xylitylglucoside, Chlorphenesin, Sodium Hyaluronate, Anhydroxylitol, Disodium Edta, Sodium Hydroxide, Yeast Extract, Xylitol, Hydrolyzed Hyaluronic Acid, Carrageenan, Caprylyl Glycol, Agar, Potassium Chloride, Xanthan Gum, Benzoic Acid, Dehydroacetic Acid, Ultramarines, Titanium Dioxide, Mica.

• Glycerin: a great humectant
• Butylene Glycol: a humectant and a solvent
• Panthenol: pro-Vitamin B5, a good barrier-repair active
• Pentylene Glycol: humectant and a preservative
• Phenoxyethanol, Chlorphenesin, Caprylyl Glycol, Benzoic acid, Dehyoacetic acid: preservatives
• Acrylates/C10-30 Alkyl Acrylate Crosspolymer: gelling agent
• Trehalose: humectant, skin conditioning
• Xylitol, Xylitylglucoside, Anhydroxylitol: (Aquaxyl) humectant, barrier-repair
• Sodium Hyaluronate: a salt form of HA
• Disodium EDTA: a chelating agent
• Sodium Hydroxide: pH adjuster
• Yeast extract: humectant
• Hydrolyzed Hyaluronic acid: lower Molecular Weight HA
• Carrageenan, Agar : viscosity control
• Ultramarines, Titanium Dioxide, Mica: Colored balls?

Skin Science Discussion Notes:

• "This is really packed with humectants; it is what a standard hydrating serum should look like. Four out of the first five ingredients are all humectants, so we know it is packed."
• "One interesting ingredient here that I don't see in others is the combo Xylitol, Xylitylglucoside, and Anhydroxylitol. This is my favourite humectant after Glycerin. It really increases hydration and decreases TEWL as per our previous tests. Buttttt… it is super tacky. It seems that they didn’t use it at a high percentage in this formulation, but it would be interesting to correlate with skin-feel as they didn’t hold back."
• "It has a pH of 5.0-5.5, which is great; no adjustments are necessary."

Formulation Discussion Summary: If serum number four went all-in with texture, this one went all-in with hydration and with little regard for how it would feel. This probably is the most humectant-packed serum among all. However, I’m not a fan of fluff; this one has colored balls (lol, why is that funny) that don’t really add anything.

Average Blind INCI Score: 7/10

Serum #7

INCI: Water, Propanediol, Glycerin, Butylene Glycol, Sodium Hyaluronate, Ammonium Acryloyldimethyltaurate/Vp Copolymer, Leuconostoc/Radish Root Ferment Filtrate, Hyaluronic Acid, Carbomer, Polysorbate 20, Palmitoyl Tetrapeptide-7, Palmitoyl Tripeptide-1, Phenoxyethanol.

• Propanediol: solvent, humectant
• Glycerin: an excellent humectant
• Butylene Glycol: a thick solvent, also a humectant
• Sodium Hyaluronate: a salt form of HA
• Ammonium Acryloyldimethyltaurate/Vp Copolymer: gelling agent
• Leuconostoc/Radish Root Ferment Filtrate: preservative
• Hyaluronic acid: humectant
• Carbomer: gelling agent
• Polysorbate-20: solubilizing agent
• Palmitoyl Tetrapeptide-7, Palmitoyl Tripeptide-1: anti-aging? Peptides
• Phenoxyethanol: preservative

Skin Science Discussion Summary:

• "This one has Glycerin and Hyaluronic acid, and some other minor humectants. It’s very minimalistic, maybe a little too much. This kind of leads me to a question we were asked once: Is it better to have many different humectants or just a few with higher concentrations? My answer is, why not both? Humectants are a broad class of ingredients, and they work differently in the skin. Some humectants act as semi-occlusives by holding water in the top layer of the skin, while others replace water inside the skin. Some humectants alter the structure of keratin to make them more accessible by water. The fact is, they all function differently; that’s why our skin produces multiple Natural Moisturizing Factors and not just a single one. The only downside is that just looking at the INCI won’t really tell you about the concentration used unless the brand tells you. As for higher concentrations, the downside is that most of the time, humectants are tacky and would feel like applying pancake syrup on your face. Anyways, it has a pH of 6.5-7.0, which is on the higher side. As you know by now, you’ll have to use a low pH product after using this. It doesn’t have a lot of buffering agents, so adjusting it would be a breeze. 

Formulation Discussion Summary: This one is simple. It has some humectants with some peptides. What makes it a bit interesting for me is the choice of preservatives: Phenoxyethanol and Leuconostoc/Radish Root Ferment Filtrate. It’s like an odd food combination that works, but it is still odd. Leuconostoc/Radish Root Ferment Filtrate is a natural preservative used by those who avoid Phenoxyethanol or Parabens, so it is surprising to see the two together. It could be that the natural preservative was a part of an active ingredient, but there isn’t any active in the formulation that would have that preservative. Maybe I’m missing something, it’s a bit weird and perplexing. 

Average Blind INCI Score: 7

 

Serum #8

INCI: Astragalus Membranaceus Root Extract, 1,2-Hexanediol, Butylene Glycol, Bis-Peg-18 Methyl Ether Dimethyl Silane, Hydroxyethylcellulose, Carbomer, Arginine.

• Astragalus Membranaceus Root Extract: an anti-inflammatory? Extract
• 1,2-Hexanediol: solvent, humectant
• Butylene Glycol: solvent, humectant
• Bis-Peg-18 Methyl Ether Dimethyl Silane: a water-dispersible silicone
• Hydroxyethylcellulose: gelling agent
• Carbomer: gelling agent
• Arginine: an amino acid, humectant 

Skin Science Discussion Notes:

• "This is a straightforward formulation."
• "I think the extract would have some natural polymers like polysaccharides that can help with hydration."
• "Hexanediol and Butylene Glycol are probably in higher concentrations too, which is good for hydration."
• The water-soluble silicone would also help in hydration and texture. It has a pH of 4.5-5.0, which is great; no adjustments are needed.

Formulation Discussion Summary:

I think this is another Korean product. That’s why the INCI is written differently. If this were to be written in FDA INCI regulations, Astragalus Membranaceus extract cannot be the first ingredient as its solvent would obviously be of higher concentration. As mentioned in Serum #2, we can’t give a proper rating on the INCI list in terms of concentration. What’s interesting here is the use of water-soluble silicone. It imparts a very luxurious and hydrating feel to the serum. I usually see this in high-end serums.

Average Blind INCI Score: 5.5

Serum #9

INCI: Aqua (Water), Hydrolyzed Yeast Extract, Glycerin, Hyaluronic Acid, Sodium Hyaluronate, Sodium Butyroyl Hyaluronate, Sodium Hyaluronate Crosspolymer, Hydrolyzed Sodium Hyaluronate, Disodium Acetyl Glucosamine Phosphate, Tetradecyl Aminobutyroylvalylaminobutyric Urea Trifluoroacetate, Pseudoalteromonas Exopolysaccharides, Tamarindus Indica Seed Gum, Tremella Fuciformis Sporocarp Extract, Ceratonia Siliqua Gum, Myristoyl Nonapeptide-3, Plantago Lanceolata Leaf Extract, Salvia Sclarea Extract, Arginine, Aspartic Acid, Glycine, Alanine, Serine, Valine, Isoleucine, Proline, Threonine, Histidine, Phenylalanine, Pca, Sodium Pca, Betaine, Sodium Lactate, Epigallocatechin Gallatyl Glucoside, Gallyl Glucoside, Algae Extract, Sodium Salicylate, Lecithin, Polyglucuronic Acid, Xanthan Gum, Trisodium Ethylenediamine Disuccinate, Sclerotium Gum, Pullulan, Cetyl Hydroxyethylcellulose, Propanediol, Pentylene Glycol, Dimethyl Isosorbide, Citric Acid, Magnesium Chloride, Silica, Polysorbate 20, Ethoxydiglycol, Propyl Gallate, Dehydroacetic Acid, Benzyl Alcohol, Potassium Sorbate, Sodium Benzoate, Ethylhexylglycerin, 1,2-Hexanediol, Caprylyl Glycol, Phenoxyethanol.

• Hydrolyzed Yeast Extract: humectant, most likely contains polysaccharides to prevent water loss
• Glycerin: an excellent humectant
• Hyaluronic acid: a humectant
• Sodium Hyaluronate: a salt form of HA
• Sodium Butyroyl Hyaluronate: a form of HA with butyrate attached to it. Manufacturer notes: longer lasting hydration? and some antioxidant? and anti-inflammatory? properties. 
• Sodium Hyaluronate Crosspolymer: a cross-linked HA
• Hydrolyzed Sodium Hyaluronate: lower MW HA
• Disodium Acetyl Glucosamine Phosphate: a synthetic building block of HA and other GAGs
• Tetradecyl Aminobutyroylvalylaminobutyric Urea Trifluoroacetate: collagen booster?
• Pseudoalteromonas Exopolysaccharides: marine hyaluronics, polysaccharides derived from marine bacteria
• Tamarindus Indica Seed Gum: also a polysaccharide
• Tremella Fuciformis Sporocarp Extract: another polysaccharide that can bind water like HA
• Ceratonia Siliqua Gum: Gelling agent
• Myristoyl Nonapeptide-3: a possible anti-aging? Peptide
• Plantago Lanceolata Leaf Extract: anti-aging? Extract
• Salvia Sclarea Extract: Clary Sage, hydrating? Extract
• Arginine, Aspartic Acid, Glycine, Alanine, Serine, Valine, Isoleucine, Proline, Threonine, Histidine, Phenylalanine, PCA, Sodium PCA: amino acids that also act as humectants
• Betaine: osmolyte and anti-irritant
• Sodium Lactate: NMF
• Epigallocatechin Gallatyl Glucoside, Gallyl Glucoside, Propyl Gallate: Glycosylated form of EGCG and Gallic acid, used here as a soothing agent
• Algae Extract: has polysaccharides, humectant
• Sodium Salicylate: salt form of salicylic acid, anti-irritant
• Xanthan Gum (and) Lecithin (and) Sclerotium Gum (and) Pullulan: Siligel, a gelling agent
• Polyglucuronic Acid: an oligosaccharide, humectant
• Trisodium Ethylenediamine Disuccinate: a chelating agent
• Cetyl Hydroxyethylcellulose: texture enhancer
• Propanediol: solvent, humectant
• Pentylene Glycol: humectant, preservative
• Dimethyl Isosorbide: penetration enhancer
• Citric acid: pH-adjuster
• Magnesium Chloride: salt, viscosity control
• Silica: texture enhancer
• Polysorbate 20: a solubilizer
• Ethoxydiglycol: penetration enhancer and a texture modifier
• Dehydroacetic Acid, Benzyl Alcohol, Potassium Sorbate, Sodium Benzoate, Ethylhexylglycerin, 1,2-Hexanediol, Caprylyl Glycol, Phenoxyethanol: preservatives 

Skin Science Discussion Notes:

• "It is a pretty solid formulation packed with multiple humectants that work differently. You have your extracts and polysaccharides that form a hydrating layer on the top surface. You have various HA MW that may penetrate different layers of the skin. You have ones that increase bound-water percentage. You also have ones that replace water."
• "This is a stellar formulation; the only thing that can be improved is to strictly control the Hyaluronic acid Molecular Weight as the lower MW HA affects the barrier status of the skin. Other than that, it is fabulous."
• "Even the pH is 4.0-4.5, which is absolutely perfect, and it is packed with buffering agents that can resist pH changes in the skin. Bravo."

Formulation Discussion Notes:

This is a super packed formulation. They carefully chose humectants that aren’t tacky, so there is no need to adjust the texture that much. Most of the polysaccharides that they use here are multifunctional. They both function in hydration and, at the same time, texture. It is an elegant formulation.

One more thing, If you look at the INCI, you’ll notice that it has eight preservatives. Does that mean that it is over preserved? No. Most of the actives they use have their own preservative systems that also need to be written in the INCI. You can’t really say that a product is "over preserved" just by looking at the INCI. To see that, you'd need to, for example, perform multiple preservative challenge tests.

Average Blind INCI Score: 8

Serum #10

INCI: Water, Hydroxyethyl Urea, Pentylene Glycol, Ppg-10 Methyl Glucose Ether, Dpg, Diglycerin, Sodium Hyaluronate, Hydrolyzed Hyaluronic Acid (Nano Hyaluronic Acid), Sodium Acetylated Hyaluronate (Super Hyaluronic Acid), Hydroxypropyltrimonium Hyaluronate (Skin Absorbent Type Hyaluronic Acid), Sodium Hyaluronate Crosspolymer (3d Hyaluronic Acid), Lactic Acid Bacterium/Hyaluronic Acid Fermented Liquid (Fermented Hyaluronic Acid) Aphanothece Sacrum Polysaccharide (Sacrum), Hydrogenated Starch Hydrolysate, Glycosyl Trehalose, Sorbitol, Triethyl Citrate, Peg-32, Carbomer, Peg-75, 2na Succinate, Propanediol, Diethoxyethyl Succinate, Potassium Hydroxide, Succinic Acid, Edta-2na, Polyquaternium-51, Capryl Hydroxamic Acid, Hydroxyethyl Cellulose, Xanthan Gum, Phenoxyethanol

• Hydroxyethyl Urea: a form of Urea, humectant
• Pentylene Glycol: humectant and preservative
• Ppg-10 Methyl Glucose Ether: humectant, emollient
• Dipropylene Glycol: humectant, emollient
• Diglycerin: a dimer of glycerin, humectant
• Sodium Hyaluronate: a salt form of HA
• Hydrolyzed Hyaluronic acid: lower MW of HA
• Sodium Acetylated Hyaluronate: a form of HA, some hydroxyl groups are replaced by acetyl groups. This imparts some lipophilicity to HA to make it adhere longer
• Hydroxypropyltrimonium Hyaluronate: a cationic form of HA, so it also adheres more to skin
• Sodium Hyaluronate Crosspolymer: a more cross-linked HA
• Lactic Acid Bacterium/Hyaluronic Acid Fermented Liquid: fermented HA
• Aphanothece Sacrum Polysaccharide: another polysaccharide from algae
• Hydrogenated Starch Hydrolysate: some soothing ability
• Glycosyl Trehalose: a sugar, humectant, stabilizer
• Sorbitol: a sugar, humectant
• Triethyl Citrate: emollient, antibacterial
• PEG-32, PEG-75: viscosity builders
• Carbomer: gelling agent
• Disodium Succinate, Succinic acid: buffer
• Propanediol: solvent, humectant
• Diethoxyethyl Succinate: water-soluble emollient
• Potassium Hydroxide: pH adjuster
• Hydroxyethyl Cellulose: Gelling agent
• Disodium EDTA: chelating agent
• Polyquaternium-51: humectant, film former
• Xanthan Gum: Gelling agent
• Capryl Hydroxamic Acid, Phenoxyethanol: preservative 

Skin Science Discussion:

• "I think this is the only hydration serum with a urea derivative in the formulation. Urea is such an excellent hydrator as it changes the structure of keratin to make it more accessible for water, thereby increasing the bound-water fraction in the skin."
• "The formulation has different forms of HA. As with the previous serum, it has hydrolyzed HA (Nano HA). This ingredient is a double-edged sword. On the one hand, it loosens up your skin, so water has more space to occupy. On the other hand, it loosens up the skin by changing the secondary structure of keratin and the lateral organization of barrier lipids."
• "So basically, the plumping action is the swelling of your skin. If your focus is barrier repair, I'd pause on this one until your barrier recovers. However, if your skin needs extra hydration, this product is perfect for that."
• It has a pH of 4.5-5.0, which is great, and it has a bunch of buffering agents to resist pH change.

Formulation Discussion Summary:

This has the perfect balance of humectancy and texture. The humectants chosen are on the hefty side but not too sticky, like panthenol, glycerin and aquaxyl. They really want the humectants to stick to your skin as they use Ppg-10 Methyl Glucose Ether, Dipropylene Glycol, Diglycerin, which adhere really well to the skin. To add to that, there are some cationic ingredients in the formulation too. Because the outermost layer of the skin is composed of keratin, and keratin is made up of amino acids that are negatively charged, these cationic ingredients would stick to the cells, smoothing out the microscopic roughness in the skin. This is basically how skin and hair conditioners work. Obviously, these ingredients would fall off later, and you have to reapply, but they do make your skin and hair super soft.

Average Blind INCI Score: 9

Serum #11

INCI: Aqua / Water / Eau, Phenoxyethanol, Calcium Pantothenate, Sodium Hyaluronate

• Phenoxyethanol: preservative
• Calcium Pantothenate: calcium form of Panthenol, skin and hair conditioner
• Sodium Hyaluronate: a salt form of hyaluronic acid

 Skin Science Discussion Notes:

• "This is a very very simple product. It has two humectants, that’s it."
• "We don’t know what the MW of HA is, but it is most likely the higher version as the serum needs to have a body or else it would be too liquidy."
• "For people who are sensitive to many things, this would be the perfect serum as it doesn’t have a lot of uncharacterized ingredients like extracts."
• "The only concern that I have is that humectants have varying ways of hydrating the skin. Having just two might not be enough, but I guess we’ll find out in the objective testing."
• "The pH is surprisingly high at 6.5-7.0; maybe they didn’t want to add any more ingredients to adjust the pH?"

Formulation Discussion Summary:

This is a very simple formulation.

Average Blind INCI Score: 5.25

 

Objective Results 

To best show the difference in hydrating ability between the serums, the objective results were displayed as a change in corneometer a.u. from the baseline for each participant. 

Serum 6 showed the greatest increase in hydration after analyzing the corneometer data and was the only one that was statistically significant. If you remember, this was also the serum that had an overwhelmingly negative response during the subjective evaluation. Many consumers turn to things like skin-feel and texture when looking for new products, but maybe this isn’t as important as we think. There is very clearly something to be said about the lack of correlation between the subjective feel of a product and its hydrating ability.  

It is also important to note that none of the corneometer measurements following product application lead to a value correlated to what we consider “normal” skin (> 40 a.u.). When taking baseline hydration measurements, all 6 participants fell into the “very dry skin” category, with hydration measurements under 30 a.u.. After the application of the products, hydration readings put participants either in the “dry skin” category (30-40 a.u.) or simply brought them slightly closer to it. While most of these products did result in some increase in hydration, it did not bring any of the participants' hydration levels near what one would consider “ideal.” Hydration serums are often not stand-alone products and are instead used to boost one's hydration levels in a routine that already includes traditional moisturizers and occlusives. 

 

Discussion

Subjective feel didn't correlate with measured hydration 

The majority of product selection is heavily based on a consumer’s subjective evaluation of their skin condition and the product itself. In a study by Akazaki et al. (1993), 174 healthy Japanese women were asked to perform a subjective evaluation of their own facial skin, rating their skin condition in a variety of categories including moisture content. The subjects’ skin was then evaluated by trained personnel and objectively analyzed using skin measurement instruments. For the objective evaluation of skin dryness, skin conductance was measured, a micro-topography of the skin surface was performed, and exfoliative cells were removed via tape stripping. Akazaki et al. (1993) found that the subjective dryness rating did not correlate with the objective measurements via conductance and exfoliative measurements. However, the conductance data did correlate well with the assessment performed by trained personnel. It was concluded that study volunteers were unable to independently assess the scaling condition of their skin independent of the moistness or dryness condition of their skin. Therefore, objective skin measurements are imperative in determining the moisture content of consumers’ skin and overall skin condition.

Guest et al. (2013) stated that although the feel of the skin post-product application is altered due to the hydration of the stratum corneum, it is the presence of the product film which also has its own textural characteristics. Immediately upon product application to the skin, a fluid film is formed on the surface of the skin. The thickness of this film significantly alters the feel of the product versus the skin’s characteristics, and the product will play a role in the feel between the treated skin and fingertip. Thus, the initial feel of a product on the skin will be largely influenced by the product’s characteristics instead of the skin’s characteristics, assuming that the product layer is thick enough to alter skin feel.

Hydration serums aren't stand-alone products 

Although the use of a serum packed with humectants has many skin benefits, it is important to note that hydration serums should not always be used as stand-alone products. Products that contain humectants should ideally be formulated with occlusive ingredients or paired with products, such as moisturizers that can provide occlusion to the skin. As humectants attract and hold water, they will pull water molecules from every source they can. Harwood et al. noted that some humectants could draw water from the dermis and move it up to the epidermis, where it will easily be lost to the environment. This will increase the transepidermal water loss (TEWL) and further dehydrate the skin. By using humectant-rich serums in combination with occlusive moisturizers, an occlusive barrier will be formed over the skin’s surface by the ingredients present in the moisturizer, reducing the rate of water evaporation from the skin. Examples of occlusive ingredients which should be paired with humectants include hydrocarbons (e.g., petrolatum), silicones, vegetable oils, animal fats (e.g. lanolin), wax esters, and sterols.

Humectants are not often packed in traditional moisturizers because humectants require large amounts of water to be solubilized. Although moisturizers do contain a large water phase, this water is required for emulsion stability. The addition of humectants to the water phase of a traditional moisturizer will result in a decrease in available water for the emulsion as most of it would have been used to solubilize the humectants. With less available water for the emulsion, the moisturizer would break down and an undesirable product texture would be obtained.      

So what can we infer from this study (albeit not being perfect)?

The only conclusion we can derive from it is that most of the hydration we get from serums appears to be gone by 2 hours if used alone. Although Serum six showed statistical significance compared to the others, an average change of 6 au doesn’t really have much clinical significance. To put things into perspective:

Corneometer reading in au	Hydration Level
< 30	Very dry skin
30-40	Dry skin
> 40	Sufficiently hydrated skin

All of the six subjects had very dry skin before application, and none of the six had sufficiently hydrated skin 2 hours after application. This underlines the importance of using hydration serums underneath a moisturizer with occlusives. 

Now let’s go back to the results of the objective test. Does this mean that number 6 is the most hydrating of all serums? Well, we can’t really conclude that just from the study we conducted. We can conclude instead that Serum six lasted the longest, possibly because of the number and amount of humectants in the formulation. Because we only measured it at 2 hours, we could’ve missed a lot of information at 30 min or at 1 hour. It would be interesting to see the results at 30 minutes, 1 hour, 1.5 hours, and 2 hours.  Likewise, it would also be interesting if we could get meaningful data if the serums were occluded.

Limitations 

There are a number of limitations present in the design of this Quick Study, here we discuss just a few of them:

1. Sample Size: The study was performed using six participants. All six participants reside in the same geographical location and have similar professions (Scientists). Thus, the study cannot draw conclusions on how the hydration serums perform in different climates and on skin exposed to a variety of environmental stressors. All study participants were also scored to have very dry skin after the initial Corneometer reading. 
2. Product Application: All 11 products were applied to one proximal anterior forearm of each participant. Each product was applied adjacent to the other on the forearm with little space between each test site. As a result, there is the possibility that the products spread beyond the application site and into adjacent test sites. Although the droppers were the same and that the subjects all dispensed a drop, the amount of product could be more standardized. Depending on the amount of pressure the participants used to dispense the product from the bottles, the amount of serum applied would vary. Each participant was also responsible for spreading the product on their skin. The spreading method was unclear, so the product may have been rubbed in more or less by different participants and applied over a larger or smaller surface area on the forearm.  
3. Controls: To establish a baseline hydration reading, Corneometer measurements were taken on the upper portion of the proximal anterior forearm. As the baseline was only recorded for one area and products were tested across the whole forearm, there may be differences in the baseline measurements which were not accounted for. If the baseline measurement varies across the arm, the calculated change in hydration level for each product would not accurately reflect the product’s hydration ability. Establishing a control site that is specific for each area of application would ensure that more definite changes in skin hydration can be determined. 
4. Blinding: All the hydration products were dispensed into clear squeeze bottles. Some of the hydration products had very distinct colours and textures which may have been known to participants from prior use. If a participant was familiar with one of the tested hydration products, they could have been biased towards that sample based on their experience with the product and/or brand name. One of the participants had also been involved in preparing the blinded samples, so some bias may have been present in their subjective ratings. This participant would have known which products were contained in each numbered bottle and the ingredient lists, so a bias may have been developed to the samples depending on the product brand name or specific ingredients. 
5. Measurements: Skin hydration measurements were taken prior to product application to establish a baseline reading and 2 hours post-application. As per the recommendations of the Corneometer manufacturer, Courage + Khazaka, skin conductance measurements can be taken as early as 30 minutes after product application. There is no general consensus in the literature on how long after application Corneometer measurements should be taken and how times vary anywhere from 2 to 6 hours between studies. Therefore, it would be beneficial to take measurements at different times (i.e., 30 minutes, 1 hour, 1.5 hours, 2 hours) post application to determine when maximum skin hydration benefits are observed for each individual product.   
6. Environment: All skin measurements for each participant were taken in the same climate-controlled room. Every participant also spent a minimum of 30 minutes in the test room prior to Corneometer measurements in order for their skin to be acclimatized to the ambient conditions. However, in the 2 hours between product applications and final skin hydration measurements, participants moved around in the laboratory facility between various rooms. Some participants also washed their hands during the waiting period, and although special care was taken not to wash any of the treated areas, water may have splashed up onto the forearm. As a result, any wind drafts, changes in temperature, sweat, or water could have had an effect on the applied products and, thus, the final changes in hydration levels. 

Future research 

Going forward, we are interested in performing further Quick Studies and designing even more rigorous studies. As this was our first Quick Study, it was an excellent learning opportunity for us to see how future experiments should be carried out. Identifying possible limitations and biases prior to starting a new experiment will allow us to account for as many variables as possible and, thus, obtain more accurate results. Regimen Lab is a constant work in progress, and our team of scientists is constantly learning to improve their work.

Our next Quick Study will involve testing the effects of individual humectants on skin hydration. Using a similar procedure as the one described here, we will be preparing individual solutions containing humectants that are most commonly used in hydration products. We are interested in seeing which humectants are most effective at increasing hydration levels along with what concentrations they should be used at for maximum skin hydration. We are also looking to explore how different combinations of humectants influence the skin and compare skin conductance measurements with those obtained after the application of single humectants. 

 

References:

Akazaki, S., Zama, M., Inoue, N., Negishi, H., Kawai, M., & Tsutsumi, H. (1993). A Relevant Study Correlating the Actual Observed Physiological Properties and a Cosmetic-User’s Subjective Evaluations of Skin. Journal of the Society of Cosmetic Chemists Japan, 27(3) 259-468. 

Guest, S., McGlone, F., Hopkinson, A., Schendel, Z. A., Blot, K., & Essick, G. (2013). Perceptual and Sensory-Functional Consequences of Skin Care Products. Journal of Cosmetics, Dermatological Science and Applications, 3, 66-78.

Harwood, A., Nassereddin, A., & Krishnamurthy, K. (2021). Moisturizers. StatsPearl Publishing. https://www.ncbi.nlm.nih.gov/books/NBK545171/