Phenylalanine at a glance

  • Essential amino acid
  • A precursor to melanin and dopamine
  • Helps skin retain moisture
  • Aids in reducing the appearance of an uneven skin tone

Phenylalanine description

Phenylalanine is what is termed as an essential amino acid, meaning that it does not occur naturally in the human body and must be provided inobtained from food. It plays an important role in the synthesis of other amino acids and is a precursor to the skin pigment melanin and the neurotransmitter dopamine. Phenylalanine is found in the seeds and sprouts of plants such as spinach, sunflowers, peanuts, and many varieties of beans. In addition to its benefit when consumed, research shows phenylalanine also has value when applied topically. As with many amino acids, it helps skin retain moisture for a more hydrated appearance. Studies also indicate that phenylalanine can aid in the reduction ohelp to visibly reducef the appearance of an uneven skin tone. This is, in part because of its connection to melanin and its ability to inhibit melanin productionhelp control its deposition in skin’s uppermost layers. Phenylalanine has been shown to be well-tolerated by skin, with no reports of adverse reactions. Usage levels of phenylalanine in cosmetics typically range from 0.00009–0.3% in rinse-off and leave-on formulas.

Phenylalanine references

  • Saudi Pharmaceutical Journal, July 2018, pages 709-718
  • British Journal of Dermatology, June 2012, pages 16-19

Peer-reviewed, substantiated scientific research is used to assess ingredients in this dictionary. Regulations regarding constraints, permitted concentration levels and availability vary by country and region.

Ingredient ratings


Proven and supported by independent studies. Outstanding active ingredient for most skin types or concerns.


Necessary to improve a formula's texture, stability, or penetration.


Generally non-irritating but may have aesthetic, stability, or other issues that limit its usefulness.


There is a likelihood of irritation. Risk increases when combined with other problematic ingredients.


May cause irritation, inflammation, dryness, etc. May offer benefit in some capability but overall, proven to do more harm than good.


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Not rated

We have not yet rated this ingredient because we have not had a chance to review the research on it.