Glycine
Also known as Glycine, Aminoacetic acid, 2-Aminoacetic acid
“CIR Expert Panel says: safe as used in cosmetics.”
Glycine (CAS 56-40-6; the only achiral, α-unsubstituted proteinogenic amino acid) is used in cosmetics as a skin- and hair-conditioning humectant and pH adjuster. The CIR Expert Panel assessed all 21 α-amino acids and their simple salts in cosmetics (Burnett et al., IJT 32(6 Suppl):41S-64S, 2013; PMID 24335967); the Panel's conclusion explicitly names Glycine as safe in the present practices of use and concentration, supported by dermal and ocular irritation/sensitization data at up to 7.5% in cosmetic products showing no adverse effects. The QRT records Glycine with Finding=S (Safe), no qualifying conditions. A clinical study (Diaz et al., PMID 34694692) found a glycine-containing amino acid complex increased skin hydration by 39% in 24 hours with no adverse events in 37 subjects, corroborating cosmetic tolerability.
Proteinogenic α-amino acid: the simplest, smallest, and the only achiral amino acid; widely distributed in all living tissues
Natural moisturizing factor (NMF) component: free amino acids including glycine are endogenous constituents of the stratum corneum that maintain skin hydration and plasticity
Humectant and skin-conditioning agent: attracts and binds water; used at concentrations of 0.0005–4% in leave-on formulations and 0.0005–4% in rinse-off products
pH adjuster and buffering agent: used as an alternative to traditional alkaline buffers in cosmetic formulations
CIR Expert Panel concluded glycine is safe as used in cosmetics in the practices of use and concentration of the 2012 safety assessment:41-64, 2013; QRT Finding=S)
FDA GRAS status (no stereocenter, not subject to L/D labeling requirements for food additives)
Low molecular weight (75.03 g/mol) facilitates skin penetration for conditioning effects
- · No known sensitization — multiple HRIPTs at 1–2.784% showed no dermal irritation or sensitization
At concentrations above 2% applied to the eye area, in vitro HET-CAM and BCOP models indicate mild to weak ocular irritant potential; human usage studies at 7.5% in pencil eyeliner showed no eye irritation over 14 days
CIR Quick Reference Table (12/2017, revised 07/2018) — Glycine row: Finding=S, Citation=IJT 32(S4):41-64, 2013
“Glycine | S | | IJT 32(S4):41-64, 2013”— QRT-122017revised072018.pdf, p. 54