Regimen Lab Skincare Encyclopedia ?

Undecylenoyl Phenylalanine

*Preliminary Lab Notes* - Full Entry Under Development

Ingredient Profile

Common Name: Undecylenoyl Phenylalanine
INCI: Undecylenoyl Phenylalanine
Source: Amino Acids
Undecylenoyl Phenylalanine Molecule

kligman ingredient evaluation

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

Regimen's Take

Undecylenoyl Phenylalanine is an amino acid derivative studied as a skin brightener. Its main action is to inhibit the activity of alpha melanocyte stimulating hormones (a-MSH). Think of MSH as the main signal that causes hyperpigmentation in the skin. By inhibiting this overactive signal, your skin won’t overproduce melanin. Undecylenoyl Phenylalanine should be used with tyrosinase inhibitors to get the full brightening effect.


  • Studies tell us to look for Undecylenoyl Phenylalanine in concentrations of .5% - 2.5%
  • Best results are obtained if combined with 5% Niacinamide and used twice daily (in conjunction with a suncreen)
  • While potent, the best results are a little slow: look for best results within 1-3 months

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

What is Undecylenoyl Phenylalanine?

Undecylenoyl Phenylalanine is a compound that includes amino acids and lipid residue, used in cosmetics and personal care products, specifically whitening formulas, to prevent skin cells from producing melanin pigmentation. Undecylenoyl Phenylalanine inhibits melanotropin, a melanin stimulator found in the skin. Melanotropin controls tyrosinase activity (tyrosinase being an essential enzyme in the production of melanin), melanin (eumalanin) synthesis and melanosome; therefore, by preventing the production of melanotropin, the pigmentation process is reduced or halted.

Clinical Studies:

A study was done to evaluate the efficacy and safety of a preparation containing undecylenoyl phenylalanine 2% in the topical treatment of solar lentigines. In total, 36 patients with solar lentigines of the hands were randomly assigned to apply the active preparation on one side and the vehicle alone on the other side, twice daily for 12 weeks. Undecylenoyl phenylalanine 2% is a novel depigmenting agent, which possibly acts as an alpha-melanocyte-stimulating hormone antagonist, thus inhibiting melaninogenesis. It achieved a significant lightening of the lesions with minimal side-effects. Most patients were satisfied with the improvement.

Clin Exp Dermatol. 2010 Jul;35(5):473-6. doi: 10.1111/j.1365-2230.2009.03605.x. Epub 2009 Oct 23.
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.