What it is
Imidazolidinyl urea is a widely used antimicrobial preservative that helps protect water-containing cosmetics, including sunscreens, from bacteria and other microbes. It is a formaldehyde-releasing preservative, meaning it works in part by slowly releasing small amounts of formaldehyde. It is often combined with other preservatives, such as parabens, to broaden coverage against both bacteria and fungi.
Safety & warnings
As a formaldehyde-releasing preservative, it can be a contact allergen for some people, and individuals with a known formaldehyde or formaldehyde-releaser allergy may wish to avoid it. Sensitivity is more likely in those with already sensitized or reactive skin; patch testing is reasonable for such users. It is used at low, regulated concentrations in finished products.
Origin & sourcing
Synthetic; it is a manufactured preservative compound.
Questions everyone asks
What does imidazolidinyl urea do?
It is a preservative that helps keep water-based products free of microbial growth, protecting both the formula and the user.
Why is it described as a formaldehyde releaser?
It works in part by slowly releasing very small amounts of formaldehyde, which provides its antimicrobial activity. People with formaldehyde sensitivity may prefer to avoid it.