Allantoin is a chemical compound naturally produced by many organisms, including animals, plants, and bacteria. It is a frequent ingredient in lotions and skin creams, as well as in oral hygiene products, cosmetics, and other toiletries. It is also used in medications for dermatological conditions including acne, impetigo, eczema, and psoriasis. It is effective at very low concentrations, usually from 0.1% to 2%.

The allantois, from which allantoin gets its name, is an embryonic excretory organ present in most mammals, except humans and higher apes, in which the compound accumulates. It is also present in plants including comfrey, sugar beet, tobacco seed, chamomile, and wheat sprouts. Herbal extract of comfrey is a popular source of allantoin. It may also be synthesized from animal urea.

Allantoin is odourless, safe, non-toxic, and non-allergenic. It is moisturising and keratolytic, meaning that it causes keratin in the skin to soften. This property helps skin to heal more quickly and to bind moisture more effectively, making products containing this substance useful for dry skin and for healing wounds, burns, and scars. It is also effective against sunburn, chapped lips, cold sores, diaper rash, and similar skin irritations.