Betaine
Also known as Trimethylglycine, TMG, Glycine betaine, N,N,N-Trimethylglycine, Lycine
“CIR Expert Panel says: safe as used in cosmetics.”
Betaine (trimethylglycine, TMG; CAS 107-43-7) is a natural zwitterionic compound that functions as an osmoprotectant, humectant, and skin-conditioning agent. The CIR Expert Panel reviewed betaine in a March 2014 final report and classified it as Safe Qualified (SQ) — safe for use in cosmetics when formulated to be non-irritating. Filatov et al. (Molecules 2024, PMID 38611819) demonstrated that trimethylglycine at a maximum tolerated concentration of 39% upregulates aquaporin-3 (AQP3) expression in skin cells, with significant improvements in skin hydration sustained over 28 days in human volunteers. Cho et al. (Food Sci Biotechnol 2017, PMID 30263674) showed betaine reduces melanin content in murine melanocytes by approximately 21% at 1 mM via suppression of tyrosinase and MITF, with no adverse effects on cell viability, positioning betaine as a potential skin-brightening agent. The ingredient has a long history of safe use as both a dietary compound (abundant in beets, wheat germ, spinach) and a cosmetic active.
Natural osmoprotectant and humectant; draws and retains moisture in the stratum corneum
Upregulates aquaporin-3 expression in skin cells, supporting trans-membrane water transport and long-term skin hydration (Filatov et al. 2024, PMID 38611819)
Anti-melanogenic activity in vitro: reduces melanin content ~21% at 1 mM via MITF/tyrosinase suppression (Cho et al. 2017, PMID 30263674)
Naturally occurring in beets, wheat germ, and spinach; long history of human dietary exposure with favorable safety profile
CIR-approved (SQ) for cosmetic use as of 03/2014 final report
- · CIR SQ classification requires formulation to be non-irritating; neat or improperly formulated concentrations may be irritating
- · High concentrations (tested up to 39%) have not raised safety signals in the Filatov 2024 study but long-term systemic dermal absorption data at such concentrations are limited
CIR Quick Reference Table (12/2017, revised 07/2018) — BETAINE row: Finding=SQ, Citation=Final report 03/2014 available from CIR
“Betaine | SQ | safe for use in cosmetics when formulated to be non-irritating | Final report 03/2014 available from CIR”— QRT-122017revised072018.pdf, p. 12