DMDM Hydantoin is a synthetic preservative used in cosmetics and personal care products to prevent the growth of bacteria, mold, and yeast. It releases formaldehyde in small, controlled amounts, which helps to extend the shelf life of products. DMDM Hydantoin is commonly found in shampoos, conditioners, lotions, and facial cleansers. It is effective in preserving product integrity but has raised concerns for causing skin irritation or allergic reactions in sensitive individuals.