Regimen Lab Skincare Encyclopedia ?


*Preliminary Lab Notes* - Full Entry Under Development

Ingredient Profile

Common Name: Silymarin
INCI: Silymarin
Source: Milk Thistle
Silymarin Molecule

kligman ingredient evaluation

Penetration: Under analysis
Biochemical Mechanism: Under analysis
Level of Evidence: Under analysis

Regimen's Take

Silymarin is a flavonoid antioxidant found in Milk Thistle (used historically as an extract for mushroom poisoning). Silymarin has very strong antioxidant properties, with several studies proving its anti-free radical potency at about 10x that of Vitamin E preventing damage from UVA and UVB exposure. It is also being studied for it's possible ability to inhibit Tyrosinase (related to hyperpigmentation). Silymarin has also been shown to reduce inhibit inflammation-driving cytokines. Studied for its ability to improve wound healing have shown it can increase collagen and GAG production driving cosmetic and anti-aging benefits. This makes Silymarin great in antioxidant serums or as a valuable ingredient in sunscreens. A huge challenge is that it has a very dark color and, if used in higher concentrations, it stains the skin yellow.


  • Shown to have an effect at concentrations as low as .1% - you'll know it's in a product by the unmistakable yellow coloring
  • Some companies are advertising the use of SIlymarin at 0.5-1% but end up with a clear serum, which in our testing is quite impossible. What we believe is happening here is Milk Thistle Extract is being used, but incorrectly called Silymarin. If you are looking for high concentration of active, look for Silybin in the INCI
  • As with any antioxidant, no single antioxidant can tackle the whole UV damage/ inflammation / etc. process - so it's best to look for Resveratrol (like any antioxidant) in combination with other antioxidants

The full Regimen Lab Skincare Encyclopedia Entry for Silymarin is in development. Check back in a few weeks for an update!

What is Silymarin?

Silymarin is a naturally occurring compound that offers anti-oxidant effects for skin that prolong cell life. The components of silymarin are: Silibinin, silydianin, and silychristin. These compounds are used to protect and treat the skin from oxidative stress caused by ultraviolet radiation.


Silymarin is an extract isolated from the seeds of milk thistle.

How does it work?

Topical application of Silibinin prior to, or immediately after, UV irradiation has been found to inhibit thymine dimer positive cell generation that UV induces in the epidermis (5). This research has also shown that terminal sunburn cell formation that is again induced by UV is inhibited too, when Silibinin is applied.

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Other benefits

Several experiments confirm that silymarin also owns anti-inflammatoryvand anticarcinogenic properties. This includes photoprotection against the sunburn response, DNA damage and non-melanoma skin cancer, by reduction of hydrogen peroxide produced by UVB in the skin, modulation of reactive oxygen species free radical-associated pathways and repair of DNA caused by UVB1. Based on that it is clear that silymarin can improve the photoprotective effect of available sunscreens against UV light.

Silymarin has also showed photoprotective abilities such as reduction of hydrogen peroxide produced by UVB in the skin, modulation of reactive oxygen species free radical-associated pathways and repair of DNA caused by UVB1.

Clinical trials

An in vivo study used Pure Silymarin (1 mg/cm2 skin area) and topically applied to mouse skin 20-25 min before UVB exposure. They found that the treatment prevented UV light-induced infiltration of inflammatory leukocytes, which are responsible for the induction of UV-induced suppression of CHS and oxidative stress, which is responsible for numerous skin disorders including photoaging and photocarcinogenesis2. - Modulation of cutaneous wound healing by silymarin in rats.

in vivo or in vitro tests does it penetrate?

An in vivo study was done to determine the ability of silymarin to be absorbed by the skin, and showed that silibilin, the most abundant and biologically active of the three components, demonstrated significant absorption into the skin of a nude mice. In addition, the study concluded that the topical application of silymarin for up to 24 hours does not cause skin irritation3.

An in vitro study was done in a tube to evaluate the effect of silymarin on collagenase, elastase and hyaluronidase activity. The results reviled that silymarin was able to effectively inhibit the activities of isolated hyaluronidase, collagenase and elastase what results in anti-aging outcome by preventing sunlight-induced damage and (photo)aging4.

Scientific consensus on effectiveness

Researches seem to reach an agreement about the fact that the treatment doses of 0.5 or 1.0 mg/cm2 of silymarin can protect skin from locally UVB-induced immunosuppression. Furthermore, the effectiveness of silymarin compared to silibilin is not statistically significant as silibilin constitutes around 90% of sylimarin and the two materials can be used interchangeably5.


Raja K Sivamani, Jared R. Jagdeo, Peter Elsner, Howard I. Maibach. (2015).Silimarin. In Cosmeceuticals and Active Cosmetics (Third edition), (pp.113-115). Boca Raton, FL. CRC Press.

Katiyar, S. K. (2002). Treatment of silymarin, a plant flavonoid, prevents ultraviolet light-induced immune suppression and oxidative stress in mouse skin. International Journal of Oncology, 21(6), 1213–1222.

Hung, C., Lin, Y., Zhang, L., Chang, C., & Fang, J. (2010). Topical delivery of silymarin constituents via the skin route. Acta Pharmacologica Sinica, 31(1), 118–126. doi: 10.1038/aps.2009.186

Vostálová, J., Tinková, E., Biedermann, D., Kosina, P., Ulrichová, J., & Rajnochová Svobodová, A. (2019). Skin Protective Activity of Silymarin and its Flavonolignans. Molecules, 24(6). doi: 10.3390/molecules24061022

Katiyar, S. K. (2005). Silymarin and skin cancer prevention: anti-inflammatory, antioxidant and immunomodulatory effects (Review). International Journal of Oncology, 26(1), 169–176.
The Skincare Encyclopedia aims to improve public understanding of the biology and chemistry of skincare. The Encyclopedia is rooted in core scientific principles and extensive research, in many cases in collaboration with the authors of the original studies referenced. This is a project of Regimen Lab, maintained by a group of multidisciplinary scientists, MDs, and researchers.