Phenylalanine

Phenylalanine is what is termed as an essential amino acid, meaning that it does not occur naturally in the human body and must be obtained 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 help to visibly reduce the appearance of an uneven skin tone. This is in part because of its connection to melanin and its ability to inhibit melanin production. 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.