Phenylalanine
Also known as Phenylalanine, L-Phenylalanine, 2-Amino-3-phenylpropanoic acid
“CIR Expert Panel says: safe as used in cosmetics.”
Phenylalanine (CAS 63-91-2; L-Phenylalanine, the only proteinogenic amino acid with a benzyl side chain) is used in cosmetics as a skin-conditioning humectant and NMF component. The CIR Expert Panel assessed all 21 proteinogenic α-amino acids and their simple salts in cosmetics (Burnett et al., IJT 32(6 Suppl):41S-64S, 2013; PMID 24335967) and concluded they are safe in the present practices of use and concentration; Phenylalanine is explicitly named in the assessment. The September 2022 CIR QRT records Phenylalanine with Finding=S (Safe), no qualifying conditions, citing IJT 32(Suppl. 4):41-64, 2013.
Proteinogenic α-amino acid with a bulky benzyl (phenylmethyl) side chain; the L-stereoisomer is endogenous to all living tissues and an essential amino acid
Natural moisturizing factor (NMF) component: free amino acids including phenylalanine are endogenous constituents of the stratum corneum that contribute to skin hydration and plasticity
Skin-conditioning humectant: attracts and binds water in cosmetic formulations through its polar amino and carboxyl groups
CIR Expert Panel concluded phenylalanine is safe as used in cosmetics in the present practices of use and concentration:41-64, 2013; QRT Finding=S, no conditions)
- · No known sensitization or irritation concerns identified in the CIR group assessment at cosmetic use concentrations
- · Phenylalanine is the precursor to tyrosine and downstream catecholamines — relevant in medical/nutrition contexts but not a cosmetic safety concern at typical use levels
CIR Quick Reference Table (September 2022) — Phenylalanine row: Finding=S, Citation=IJT 32(Suppl. 4):41-64, 2013
“Phenylalanine | S | | IJT 32(Suppl. 4):41-64, 2013”— QuickReferenceTable_AllConclusionTypes.pdf, p. 399