Allantoin
Allantoin is a substance that is endogenous to the human body and also found as a normal component of human diets. In healthy human volunteers, the mean plasma concentration of allantoin is about 2-3 mg/l. During exercise, the plasma allantoin concentration rapidly increases about two fold and remains elevated. In human muscle, urate is oxidized to allantoin during such exercise. The concentration of allantoin in muscles increases from a resting value of about 5000 ug/kg to about 16000 ug/kg immediately after short-term exhaustive cycling exercise.   More specifically, allantoin is a diureide of glyoxylic acid that is produced from uric acid. It is a major metabolic intermediate in most organisms. Allantoin is found in OTC cosmetic products and other commercial products such as oral hygiene products, in shampoos, lipsticks, anti-acne products, sun care products, and clarifying lotions. Allantoin has also demonstrated to ameliorate the wound healing process in some studies.