Allantoin is a chemical compound with formula C4H6N4O3. It is also called 5-ureidohydantoin or glyoxyldiureide. It is a diureide of glyoxylic acid. Named after the allantois, an amniote embryonic excretory organ in which it concentrates during development in most mammals except humans and higher apes, it is a product of oxidation of uric acid by purine catabolism. After birth, it is the predominant means by which nitrogenous waste is excreted in the urine of these animals. In humans and higher apes, the metabolic pathway for conversion of uric acid to allantoin is not present, so the former is excreted. Recombinant rasburicase is sometimes used as a drug to catalyze this metabolic conversion in patients. In fish, allantoin is broken down further (into ammonia) before excretion. Allantoin is a major metabolic intermediate in many other organisms including plants and bacteria.
Allantoin is present in botanical extracts of the comfrey plant and uric acid from cows, most mammals. Chemically synthesized bulk allantoin is natural-identical, safe, non-toxic, compatible with cosmetic raw materials, and meets CTFA and JSCI requirements. Over 10,000 patents reference allantoin. Manufacturers cite several beneficial effects for allantoin as an active ingredient in over-the-counter cosmetics: a moisturizing and keratolytic effect, increasing the water content of the extracellular matrix and enhancing the desquamation of upper layers of dead skin cells, increasing the smoothness of the skin; promotion of cell proliferation and wound healing; and a soothing, anti-irritant, and skin protectant effect by forming complexes with irritant and sensitizing agents. It is frequently present in toothpaste, mouthwash, and other oral hygiene products, in shampoos, lipsticks, anti-acne products, sun care products, and clarifying lotions, various cosmetic lotions and creams, and other cosmetic and pharmaceutical products. Allantoin has not been proven scientifically to reduce the appearance of aging.