DMDM Hydantoin
What It Is
DMDM hydantoin (1,3-dimethylol-5,5-dimethylhydantoin) is a synthetic preservative in the formaldehyde-releasing preservative (FRP) class (CAS 6440-58-0). It is a white crystalline powder that dissolves readily in water. DMDM hydantoin functions as an antimicrobial preservative by slowly releasing formaldehyde into the product over time. It is one of the most commonly used FRPs in personal care products.
Common Uses
DMDM hydantoin is used in shampoos, conditioners, body washes, hair styling products, skin care creams, and some household cleaning products. It is popular in personal care formulations because it is effective at low concentrations (typically 0.1%-0.6%), compatible with a wide range of formulation types, and inexpensive. A 2019 class-action lawsuit against a major personal care brand brought significant consumer attention to DMDM hydantoin's formaldehyde-releasing properties, accelerating reformulation efforts across the industry.
How It Works
DMDM hydantoin works by releasing free formaldehyde through a reversible equilibrium reaction with water. The hydantoin ring structure acts as a reservoir, gradually releasing formaldehyde as existing free formaldehyde is consumed by antimicrobial action or dissipates. The formaldehyde released cross-links microbial proteins and nucleic acids, providing broad-spectrum preservation against bacteria and fungi.
The rate and amount of formaldehyde release depend on pH, temperature, and the concentration of DMDM hydantoin in the formulation. At typical use concentrations, free formaldehyde levels in the product generally remain below 0.1% -- but they are continuously replenished as long as unreacted DMDM hydantoin remains in the formula.
Safety and Regulation
The CIR Expert Panel concluded in 2008 that DMDM hydantoin is safe as a cosmetic ingredient at concentrations up to 0.6% when formulated to not release formaldehyde above safe levels (CIR, 2008). The EU Cosmetics Regulation permits DMDM hydantoin as a preservative with the requirement that products containing it must be labeled "contains formaldehyde" if the total free formaldehyde content exceeds 0.05%.
The primary concern is chronic low-level formaldehyde exposure. While each individual product may release formaldehyde at levels below regulatory thresholds, cumulative exposure from multiple formaldehyde-releasing products (shampoo, conditioner, body wash, moisturizer) is difficult to assess. Formaldehyde is also a well-documented contact allergen -- it is one of the most frequently positive allergens in standard patch-testing series (Warshaw et al., 2015).
Why Natural Flower Power Does Not Use It
Natural Flower Power does not use DMDM hydantoin in any product.
DMDM hydantoin releases formaldehyde -- a known human carcinogen -- as its mechanism of action. Regardless of whether the released amounts are below regulatory thresholds in any single product, we do not see a reason to introduce a carcinogen-releasing ingredient into household cleaning products when effective alternatives exist. Our BIT-based preservation system provides equivalent broad-spectrum protection without releasing formaldehyde at any concentration. This is a straightforward formulation choice, not a complex risk calculation.
Related Ingredients
Formaldehyde is the active antimicrobial substance released by DMDM hydantoin. Quaternium-15 is another formaldehyde-releasing preservative that releases more formaldehyde per unit weight than DMDM hydantoin. Imidazolidinyl urea and diazolidinyl urea are other FRPs with similar mechanisms. Benzisothiazolinone (BIT) is the preservative Natural Flower Power uses instead.
Sources
- Cosmetic Ingredient Review (CIR). "Safety Assessment of DMDM Hydantoin as Used in Cosmetics." 2008 review.
- Warshaw, E.M., et al. "Patch Testing with North American Contact Dermatitis Group Standard Series." Dermatitis, vol. 26, no. 1, 2015, pp. 49-59.
- National Toxicology Program. "14th Report on Carcinogens: Formaldehyde." 2016.
