Allantoin

Also known as 5-Ureidohydantoin, (2,5-Dioxo-4-imidazolidinyl)urea, Glyoxyldiureide, Alantan

Allantoin (5-ureidohydantoin; (2,5-dioxo-4-imidazolidinyl)urea; CAS 97-59-6; C4H6N4O3) is a small heterocyclic molecule that occurs naturally in comfrey root, chamomile, and as a metabolite of uric acid in most mammals (but not humans, who lack urate oxidase and instead excrete uric acid directly). In cosmetic formulations it functions as a skin conditioning agent with well-documented soothing, keratolytic, and wound-healing-support properties. The CIR Expert Panel assessed allantoin together with 6 related complexes (allantoin ascorbate, allantoin biotin, allantoin galacturonic acid, allantoin glycyrrhetinic acid, allantoin panthenol, and allantoin polygalacturonic acid) and concluded that these ingredients are safe in the product categories and concentrations reviewed (Becker, Bergfeld, Belsito et al., Final Report of the Safety Assessment of Allantoin and Its Related Complexes, Int J Toxicol 29(Suppl 2):84-97, 2010, PMID 20448269). At the time of the assessment, allantoin was reported in 1,376 cosmetic products at concentrations up to 2%. The assessment noted that several of the complexes (allantoin ascorbate, allantoin biotin, allantoin glycyrrhetinic acid, allantoin panthenol) incorporate active ingredients that had already been individually determined safe by the CIR Panel in prior assessments. The QRT row carries no conditions or concentration limits. Allantoin is widely used in post-procedure skincare, diaper rash products, after-sun formulations, sensitive-skin moisturizers, and wound care — it pairs well with other soothing actives like panthenol and bisabolol.