DMDM Hydantoin

dee-em-dee-em hy-DAN-toh-in

Preservative 3/10 Safety Not CGAvoid Synthetic Vegan

What Is DMDM Hydantoin?

DMDM Hydantoin is a formaldehyde-releasing preservative used to prevent microbial growth in hair care products. It slowly releases small amounts of formaldehyde over time to maintain antimicrobial protection. It gained widespread negative attention after a 2021 lawsuit against a major hair care brand alleged it caused hair loss, leading many brands to reformulate.

Source: Chemically synthesized

Origin: Synthetic

Also known as: Dimethylol Dimethyl Hydantoin, Glydant, 1,3-Dimethylol-5,5-Dimethylhydantoin

What Does DMDM Hydantoin Do to Your Hair?

DMDM Hydantoin preserves cosmetic products by slowly releasing formaldehyde, which kills bacteria, yeast, and mold. The formaldehyde is released in small, controlled amounts to maintain product sterility over the shelf life. While effective as a preservative, it is the formaldehyde release that has made it controversial.

Best For

None recommended due to controversy

Not Recommended For

All hair types, especially sensitive scalp, those with formaldehyde sensitivity

Concentration Matters

0.1-0.6%

Hair Type Compatibility

1A Straight Fine
1B Straight Medium
1C Straight Coarse
2A Wavy Fine
2B Wavy Medium
2C Wavy Coarse
3A Curly Loose
3B Curly Tight
3C Curly Corkscrew
4A Coily S-Shaped
4B Coily Z-Shaped
4C Coily Tight

Method Compatibility

Curly Girl (CG) Method: Avoid
CG Avoid

Safety & Regulation

3/10
AvoidCautionSafe

Releases formaldehyde, a known carcinogen (IARC Group 1). Can cause scalp irritation, contact dermatitis, and allergic reactions. The 2021 class-action lawsuit against TRESemme alleged hair loss from DMDM Hydantoin exposure. While the amount of formaldehyde released is small, cumulative exposure from multiple products is a concern.

FDA Status: Generally Recognized As Safe

FDA permits use in cosmetics but has issued guidance on formaldehyde in cosmetics. EU permits DMDM Hydantoin up to 0.6% with mandatory labeling if free formaldehyde exceeds 0.05%. CIR considers safe up to 0.6% in cosmetics.

EWG Score: 7/10

HairAide Verdict

DMDM Hydantoin is an ingredient HairAide recommends avoiding. While regulatory agencies consider it safe at approved levels, the fact that it releases a known carcinogen makes it unnecessary when effective alternatives exist. Many major brands have already reformulated to remove it. Choose products preserved with phenoxyethanol or sodium benzoate instead.

Products That Contain DMDM Hydantoin

Shampoos, conditioners, styling products, body washes

Alternatives to DMDM Hydantoin

If you want to avoid DMDM Hydantoin, look for products with these ingredients instead:

Phenoxyethanol, Sodium Benzoate, Potassium Sorbate, Ethylhexylglycerin

Frequently Asked Questions

Is DMDM Hydantoin safe for hair?

DMDM Hydantoin has a safety rating of 3/10 and may be problematic for many hair types. Releases formaldehyde, a known carcinogen (IARC Group 1). Can cause scalp irritation, contact dermatitis, and allergic reactions. The 2021 class-action lawsuit against TRESemme alleged hair loss from DMDM Hydantoin exposure. While the amount of formaldehyde released is small, cumulative exposure from multiple products is a concern.

Is DMDM Hydantoin bad for curly hair?

DMDM Hydantoin is not CG-method approved. Curly hair types may want to avoid this ingredient or use products containing it sparingly.

Is DMDM Hydantoin CG-method approved?

No, DMDM Hydantoin is not approved for the Curly Girl method.

What can I use instead of DMDM Hydantoin?

Some alternatives to DMDM Hydantoin include: Phenoxyethanol, Sodium Benzoate, Potassium Sorbate, Ethylhexylglycerin

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