Keratolytic. Diureide of glyoxylic acid produced from uric acid by the enzyme uricase. In most animals (not in humans) it is the end product of the purine metabolism. Allantoin is found in a small number of plants, such as Symphytum offcinale (comfrey), horse chestnut bark and wheat germ.
Allantoin is soluble in cold water up to 0.5%, in hot water up to 4%.