Safety assessment of xylitol used in cosmetic products

Xylitol is widely used as a humectant and a skin-conditioning agent in cosmetics. In this review, the toxicological profile of xylitol, including acute toxicity, repeated-dose toxicity, skin irritation, skin sensitization, reproductive and developmental toxicity, genotoxicity, carcinogenicity, phototoxicity, and toxicokinetics, was evaluated. The LD₅₀ values were reported as 4 g/kg body weight (bw) in rats and 25 g/kg bw in rabbits, indicating a low level of acute toxicity. In skin irritation studies, formulations containing 10% xylitol in both cream and gel were classified as non-irritant to the skin. In human repeat insult patch tests, xylitol did not induce sensitization reactions at concentrations up to 3%. In a 13-week repeated oral dose toxicity study in rats, the no-observed-adverse-effect level (NOAEL) was established at 20 g/kg bw/day, the highest dose tested. In a three-generation reproductive toxicity study in rats, xylitol up to 20% did not produce adverse effects on reproductive performance, fertility, or developmental outcomes across three generations. In vitro genotoxicity tests, including Ames tests, chromosome aberration tests, and sister chromatid exchange assays, showed negative results. In an in vivo micronucleus assay in mice, oral administration of xylitol at doses up to 5333 mg/kg bw resulted in no statistically significant increase in micronucleated erythrocytes. In carcinogenicity studies, although cases of urinary bladder calculi and tumors were reported at high dietary concentrations (10-20%), no causal relationship with carcinogenicity was established. The potential for phototoxicity of xylitol under actual use conditions was considered low. The systemic exposure dose of xylitol was calculated to be 7.042 mg/kg/day, assuming a 5% use level in cosmetic products. A margin of safety was calculated to be greater than 100, suggesting that the use of xylitol as a cosmetic ingredient is safe under current conditions of use.