DMDM Hydantoin and Hair Loss: What the Research Shows

DMDM hydantoin is a preservative that releases small amounts of formaldehyde, and it is common in the online conversation about shampoo and hair loss. We found no study showing that DMDM hydantoin causes hair loss. The research is about skin allergy: it can trigger contact dermatitis in people already allergic to formaldehyde.

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Key Takeaways

• We found no study linking DMDM hydantoin to hair loss.
• In a patch-test study, 8 of 14 formaldehyde-allergic people reacted to DMDM hydantoin, and 4 of 12 developed dermatitis from a cream with 1% of it.
• A 2023 quantitative risk assessment concluded that shampoos with DMDM hydantoin at or below current allowable concentrations are not expected to increase the risk of skin sensitization in healthy individuals.
• A multicenter surveillance study reported on contact allergy to DMDM hydantoin from 1994 to 2000.

What Is DMDM Hydantoin?

It is a preservative used in cosmetics and shampoos that works partly by releasing formaldehyde. Because formaldehyde can sensitize skin, researchers have studied how often it causes allergic reactions.

Does It Cause Hair Loss?

Not shown. Allergic scalp reactions can make skin itchy or inflamed, but we found no study connecting it to hair loss.

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If You're Concerned

• Read the ingredient list, and look for DMDM hydantoin or "formaldehyde releaser" on the label.
• Stop using a product that irritates your scalp, and see a doctor if irritation lasts.
• See a doctor for hair loss. There are many causes, and they can look at yours.

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What The Research Shows

Patch Tests In Formaldehyde-Allergic People

Researchers patch-tested 35 formaldehyde-allergic patients and found that 57% (8 of 14) of those tested reacted to DMDM hydantoin at one or more concentrations. When 12 such patients applied a cream with 1% DMDM hydantoin for a week, 4 (33%) developed dermatitis. The authors concluded that cosmetic concentrations contain enough free formaldehyde to cause dermatitis in some formaldehyde-allergic people (de Groot et al., 1988).

Risk In Shampoos

A quantitative risk assessment looked at shampoos containing the maximum allowable 1% DMDM hydantoin, equal to 0.02% free formaldehyde. It found a margin of safety above 1 for typical use, indicating a low likelihood of skin sensitization induction among healthy individuals, and concluded shampoos at or below allowable concentrations are not expected to increase that risk (Stewart et al., 2023).

Contact Allergy Surveillance

A multicenter study from the German contact dermatitis network reported on contact allergy from DMDM hydantoin between 1994 and 2000. PubMed doesn't include an abstract for it, so we can only report its title and scope (Uter et al., 2002).

Preservatives are a common question; see also caprylhydroxamic acid.

See also: Nickel and Hair: Allergy, Diet & Hair Analysis · Astaxanthin for Hair: What the Research Shows

Frequently Asked Questions

Does DMDM hydantoin cause hair loss?

We found no study showing that.

Is DMDM hydantoin safe?

A risk assessment found shampoos at allowable levels are not expected to raise sensitization risk in healthy people, but people allergic to formaldehyde may react.

How do I know if I'm allergic?

A doctor can arrange patch testing.

References

1. de Groot AC, van Joost T, Bos JD, et al. Patch test reactivity to DMDM hydantoin. Relationship to formaldehyde allergy. Contact Dermatitis. 1988. PubMed
2. Stewart CK, Parker J, Hwang R, et al. Quantitative Risk Assessment of Dermal Sensitization Potential Following Use of Shampoo Products Containing the Formaldehyde Releasing Preservative DMDM Hydantoin. Int J Toxicol. 2023. PubMed
3. Uter W, Frosch PJ, IVDK Study Group and the German Contact Dermatitis Research Group, DKG. Contact allergy from DMDM hydantoin, 1994-2000. Contact Dermatitis. 2002. PubMed