DMDM hydantoin is a preservative and antimicrobial agent found in a wide range of cosmetics and skin-care and hair-care products. It's considered a “formaldehyde donor.” That means it releases a small amount of formaldehyde over time to help keep products fresh and free from contaminants.

 It is used in the cosmetics industry and found in products like Hand wash, shampoo, hair conditioners, hair gels, Rite Aid Liquid Lubricant, and skin care products. DMDM hydration works as a preservative because the released formaldehyde makes the environment less favourable to the microorganisms.