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. Allantoin 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, expect humans and higher apes, in which the compound accumulates. Animals produce allantois as a byproduct of purine catabolism, in which the waste product uric acid is oxidized and broken down. 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 odorless, safe, non-toxic, and non-allergenic in both natural and chemically synthesized form. When sold on its own for use in homemade soaps, lotions, and bath products, allantoin is a white, crystalline powder. Allantoin is moisturizing 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 allantoin 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.

Those without specific skin problems can also benefit from products containing allantoin, as they help keep the skin soft, smooth, and healthy. Allantoin also helps protect the skin against irritants, and may be added to cosmetic products in order to counteract the drying or irritating effects of other ingredients, such as soap, detergents, alcohols, or acids. People with sensitive skin may therefore prefer products with allantoin. The compound has not been proven to reduce the effects of aging, however.