Urea, also known as carbamide, is a nitrogen-containing compound the body produces when it breaks down proteins. Once urea is formed from protein breakdown, it's excreted into the urine and through sweat as a waste product. In addition, ammonia in the body is broken down to form urea and eliminated through the urine.
Urea has a variety of commercial uses and is an ingredient in some skin care and cosmetic products, although urea used in products is usually made synthetically and doesn't come from urine. In fact, urea was the first natural compound to be made through synthetic means. Synthetic urea is usually white in color or clear and comes in the form of a powder, crystal or pellet.
One of the most common ways urea is used is as a fertilizer. Urea offers advantages as a fertilizer since it doesn't pose a fire hazard or release pollutants into the environment. It's also used to manufacture resins, adhesives, animal feed and is a flavor-enhancer in cigarettes. In addition, it may be used for deicing roads, flame-proofing materials and as an ingredient in pharmaceutical products and cold packs applied to the skin. Some home care products like toilet bowl cleaners also contain urea.
Urea is also an ingredient in some cosmetic and personal care products, especially moisturizers. This is due to its ability to act as a humectant. Humectants attract water to the skin from the atmosphere when the humidity level is high. This helps to hydrate the skin and keep it moist. When humectants are combined with other moisturizing ingredients called occlusive that trap water, it creates the ideal moisturizer. When humectants like urea draw water to the skin it helps to "plump up" the skin surface. This makes fine lines and wrinkles look less noticeable. It's also a component of "natural moisturizing factor," skin's natural defense against moisture loss.
Urea has other functions in cosmetic and skin care products as well. It helps to prevent moisture loss when added to products so that the consistency doesn't thicken over time. It also helps preserve their acid-base balance. In addition urea increases the ability of other skin care ingredients to penetrate the skin, For example, using a urea-based product with another ingredient like a retinol helps retinol better penetrate the epidermis.
At higher concentrations, urea also acts as a keratolytic by dissolving the keratin that holds the outer layer of skin cells together. This helps to reveal the healthier skin underneath and reduce skin roughness. It also has antimicrobial activity, which makes it an effective preservative that increases the shelf life of products. Due to its keratinolytic activity, moisturizers that contain urea are effective for treating skin conditions like psoriasis, and at higher concentrations, corns and calluses. At concentrations of 40% or greater, it can be used to chemically soften and remove a damaged nail without surgery. This includes ingrown nails and nails damaged from a fungal infection. Cosmetically, urea can be found in a wide range of products including facial moisturizers, body lotions, bath oils, hair care products, hair removers, tooth whiteners, foundation, eye shadow, makeup removers, baby wipes and cuticle removers.
Is it safe? Urea appears to be safe in the quantities found in cosmetic and skin care products, but it can be irritating to the skin at higher concentrations. Some people experience temporary itching, burning, stinging, irritation or flaking when they use products that contain urea concentrations of 20% or greater. Allergic reactions to urea-based products are also possible but aren't common. The United States Food and Drug Administration classifies urea as "generally recognized as safe" as a direct food additive.
All in all, urea is an effective humectant that helps to draw water to the skin to keep it hydrated. It makes an ideal moisturizer when combined with an occlusive or emollient that holds in water. Urea is also a mild keratinolytic that makes it helpful for treating certain skin conditions like psoriasis as well as corns and calluses. In addition, cosmetic manufacturers use it help their products perform better.