DMDM Hydantoin

Also known as: Dimethylol dimethyl hydantoin, DMDMH, Glydant

A formaldehyde-releasing cosmetic preservative whose main practical concern is contact allergy in susceptible users.

Editorial review by the IngredientWiki Editorial Team
Updated 2026-09-28
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Clear cosmetic liquid and an unlabelled laboratory vial in a paper collage — Editorial illustration

DMDM hydantoin is a water-soluble preservative that slowly releases small amounts of formaldehyde to control microbes in cosmetics. Safety assessments address use concentration and total formaldehyde exposure, while dermatology literature confirms that the ingredient can matter for people allergic to formaldehyde or its releasers.^{2, 3, 1}

Used to prevent bacterial and fungal growth^{1, 2}
Releases formaldehyde gradually inside the formula^{1, 2}
Contact allergy is the key consumer concern^{1, 2}
It is not evidence that a product is contaminated^{1, 2}

What is DMDM Hydantoin?

DMDM hydantoin is a preservative, not a conditioning active. It extends product safety by maintaining antimicrobial protection after a container is opened and repeatedly exposed to hands, water, and air.^{1, 2}

Where it comes from

Natural sources

Not a naturally harvested cosmetic ingredient

How it's made

Manufactured as a defined hydantoin-based preservative and supplied in controlled aqueous systems.

What it does in products

Benefits

Microbial control

moderate evidence

Its benefit is preservation of the finished formula rather than a direct effect on skin or hair.^{2, 1}

Preservative function and historical use are established; safety still depends on concentration and the whole preservation system.

Lower single-use microbial exposure

moderate evidence

A functioning preservative system reduces growth introduced during normal product use.²

This is a product-safety function, not a clinical treatment claim.

Suitable for formaldehyde-allergic users

insufficient evidence

People with confirmed allergy may react and should not assume a low concentration is personally tolerated.^{3, 2}

Population-level safety conclusions do not override individual patch-test results.

Evidence scope and limitations

Cosmetic preservation, formaldehyde release, irritation, and contact allergy are covered; occupational and inhalation exposures are outside the page scope.

Reaction risk depends on personal sensitization and total formulation exposure.
Older safety assessments do not predict every modern product format.

Evidence last checked: 2026-09-28

Side effects & safety

Allergic contact dermatitis (uncommon)Risk is higher in people already sensitized to formaldehyde or formaldehyde releasers.

Irritation (uncommon)Depends on concentration and finished formulation.

Safety considerations

No pharmacologic interactions expected from ordinary cosmetic use
Not for: Confirmed formaldehyde or DMDM hydantoin contact allergy
Not for: Use on actively inflamed skin if the product stings

^{2, 3}

Amounts studied & product use

These figures describe research or common product use, not a personal dose or treatment recommendation.

In skincare studies and products

Preservative levels are set by the manufacturer and safety assessment of the complete formula. Consumers should not add raw DMDM hydantoin to products or infer safety from percentage alone.

Regulatory status

Permitted as a cosmetic preservative in the United States; manufacturers remain responsible for product safety and truthful labeling.
INCI name on cosmetic labels: DMDM Hydantoin.
CIR has assessed DMDM hydantoin in cosmetic use, including formaldehyde release and sensitization data.

^{4, 2}

Formaldehyde releaser does not mean the bottle contains embalming fluid

The relevant question is the amount of free formaldehyde available from the preservation system and whether a user is sensitized. The chemistry, exposure, and finished formula matter more than the alarm value of the word formaldehyde.

^{2, 3}

Frequently asked questions

Does DMDM hydantoin contain formaldehyde?

It releases small amounts over time; safety assessment considers the resulting exposure, not just the ingredient name.^{2, 3, 1}

Should everyone avoid it?

No. The clearest reason to avoid it is confirmed allergy or a reaction to the finished product.^{2, 3, 1}

Why use it in shampoo?

Water-rich products need preservation against microbes introduced during storage and use.^{2, 3, 1}

The bottom line

DMDM hydantoin preserves products effectively, but formaldehyde-allergic users have a specific, evidence-based reason to check labels.

References

DMDM hydantoin: compound summary. PubChem, National Library of Medicine (2026) · ingredient monograph · CID 22947
Final report on the safety assessment of DMDM hydantoin. Cosmetic Ingredient Review (1988) · safety assessment
Contact allergy to and allergic contact dermatitis from formaldehyde and formaldehyde releasers: a clinical review and update. Contact Dermatitis (2022) · other · PMID 35229319
FDA Authority Over Cosmetics: How Cosmetics Are Not FDA-Approved, but Are FDA-Regulated. U.S. Food and Drug Administration (2013) · government guidance

Revision history

2026-09-28Initial publication with claim-level citations, formulation limits, safety context, and editorial evidence review.