What is it?
When discussing urea in skincare, we are not talking about urea from human or animal urine, nor synthetic and carbon dioxide combinations are used in fertilizers, plywood, and explosives. Yet how and why would any form of urea be used in skincare products?
Urea may be listed as DMDM Hydantoin, Diazolidinyl Urea, Imidazolidinyl Urea and Poloxymethylene Urea, and are mainly used as preservatives. Synthetic urea is also used in some skin creams and moisturizers, tooth whiteners and dish soap for its water-binding and exfoliating properties. It is also the main ingredient in depilatory hair removers due to its ability to break down (denature) protein. The CIR deemed urea safe for use in cosmetics with qualifications subject to concentration and use limitations and The Scientific Committee on Cosmetic Products and Non-Food Products (SCCPNP) concurred.
However, urea is believed to have a high concentration of formaldehyde and release formaldehyde and when used topically is shown to be an extreme eye, skin and respiratory irritant with the possibility of being toxic to the blood, cardiovascular system and organs with prolonged exposure so better to avoid it.
Types of Urea
DMDM hydantoin is the form of most concern, according to some sources that give it the highest overall concern rating due to the formaldehyde it releases. There is strong evidence that it is a skin irritant, toxicant and allergen, according to CIR. It also is linked with allergies and immunotoxicity and restricted for use in Japan.
Some sources indicate that both diazolidinyl urea and imidazolidinyl urea are proven to release methylene glycol, the alcohol form of formaldehyde, a gas known to irritate the skin and body. However, others only list imidazolidinyl urea as the main form to avoid.
Diazolidinyl urea is listed as causing allergies and being a toxicant for the skin yet deemed safe for use by the CIR and Scientific Committee on Cosmetic products and Non-Food Products. There was limited evidence to it causing cancer according to the International Agency for Research on Cancer.
Imidazolidinyl Urea is suspected of causing allergies, being a toxicant for the skin and body, in addition to significant concern about it releasing formaldehyde, a known carcinogen into a product. Consequently, urea and urea hydrogen peroxide have been restricted for use in cosmetics in Canada.