Diazolidinyl urea, 1-[1,3-bis(hydroxymethyl)-2,5-dioxo-4-imidazolidinyl]-1,3-bis(hydroxymethyl)urea is an antimicrobial preservative used in cosmetics. It is chemically related to imidazolidinyl urea which is used in the same way. It is used in many cosmetics, skin care products, shampoos and conditioners, as well as a wide range of products including bubble baths, baby wipes and household detergents.

Imidazolidinyl Urea is an odorless white powder. In cosmetics and personal care products, Imidazolidinyl Urea can be found in many product types including lotions, creams, hair conditioners, shampoos and deodorants.Imidazolidinyl Urea kills microorganisms, or prevents or inhibits their growth and reproduction. Preventing the growth of microbes protects cosmetics and personal care products from spoiling.

Imidazolidinyl Urea is one of the most frequently used preservatives in cosmetics and personal care products. It acts synergistically with other preservatives resulting in a system that gives a wider range of protection against microorganisms.

What it does
Diazolidinyl Urea is a preservative that prevents bacterial growth. It works by releasing small amounts of formaldehyde.
Side effects
Although Diazolidinyl releases toxic formaldehyde, the amounts are too small to pose a threat to human health. The Cosmetic Ingredient Review (CIR) Expert Panel considers Diazolidinyl Urea safe to be used in cosmetics up to a maximum concentration of 0.5%. In Europe, when the concentration of formaldehyde in the finished product exceeds 0.05%, the labels has to state "contains formaldehyde".
However, Diazolidinyl Urea can cause irritations and allergies.

Stability:  Stable. Incompatible with strong oxidizing agents.