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Diazolidinyl Urea

A formaldehyde-releasing preservative, not the moisturizing urea used for dry or rough skin.

Pencil and watercolor drawing of an amber jar and powder tray
Editorial illustration

Diazolidinyl urea preserves products by releasing formaldehyde. It is not interchangeable with plain urea in a moisturizer. People allergic to formaldehyde or to this particular preservative can develop contact dermatitis; the full ingredient name is therefore more useful than the word urea alone.1, 2

  • A formaldehyde-releasing cosmetic preservative.1
  • Different from plain urea and from imidazolidinyl urea.1, 2
  • Individual releasers can need separate diagnostic patch testing.1

What is Diazolidinyl Urea?

Preservatives can help prevent a product from deteriorating, while also being relevant contact allergens. Those are not contradictory statements. Diazolidinyl urea belongs to the formaldehyde-releaser group, but allergy to the releaser itself and allergy to formaldehyde do not always produce identical testing results.2

Where it comes from

Natural sources

  • Not a source of dietary or natural skin-moisturizing urea.

How it's made

Manufactured preservative with formaldehyde-releasing chemistry.

What it does in products

  • Microbial preservation

Benefits

Product preservation, not moisturization

limited evidence

Its purpose is to help preserve a formula. It should not be credited with the keratolytic or moisturizing uses of plain urea.1, 2

The sources are a clinical allergy review and a government hazard assessment. They do not demonstrate a direct skin-treatment benefit from this preservative.

Evidence scope and limitations

Diazolidinyl urea as a formaldehyde-releasing preservative, focused on human contact allergy and cosmetic exposure.

  • The cited review does not estimate an individual's risk from a particular product.
  • Hazard and diagnostic patch-test data are not consumer dose guidance.

Evidence last checked: 2026-10-01

Side effects & safety

Allergic contact dermatitis (varies)Reactions can reflect formaldehyde sensitivity, sensitivity to the specific releaser, or both.

Safety considerations

  • Formaldehyde release is affected by product chemistry and conditions; an ingredient list alone cannot calculate exposure.
  • Not for: People with diagnosed formaldehyde allergy should discuss avoidance of formaldehyde releasers with their clinician.
  • Not for: Avoid diazolidinyl urea after a confirmed positive reaction to this preservative.
1, 2

Amounts studied & product use

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

In skincare studies and products

Preservation levels and release conditions are manufacturer-level questions. The cited clinical review's patch-test concentrations are diagnostic procedures, not cosmetic use recommendations or instructions for home testing.

1

Regulatory status

  • Subject to U.S. cosmetic safety requirements; a preservative role is not FDA approval to treat skin disease. The Australian hazard assessment is not a U.S. concentration rule.
  • INCI name on cosmetic labels: Diazolidinyl Urea.
3, 2

A negative formaldehyde test does not answer every allergy question

A person can react to a particular formaldehyde releaser even when testing for formaldehyde is negative. The 2022 review recommends considering the specific releasers in diagnostic assessment.

For someone without a diagnosed allergy, the name alone cannot predict an individual reaction. For someone with confirmed sensitization, simply changing from one releaser to another may not resolve the exposure problem.

1

Frequently asked questions

Is it the same as the urea in a foot cream?

No. Diazolidinyl urea is a preservative with formaldehyde-releasing chemistry. A plain urea treatment claim cannot be assigned to it.2

Can I patch-test the raw preservative at home?

No. Clinical diagnostic test preparations and interpretation are not DIY procedures. A raw preservative is not a finished cosmetic.1

The bottom line

Read the complete name and use a confirmed allergy history to guide avoidance. Plain urea and diazolidinyl urea are different ingredients.

References

  1. Goossens A, Aerts O. Contact allergy to and allergic contact dermatitis from formaldehyde and formaldehyde releasers: A clinical review and update. Contact Dermatitis (2022) · other · PMID 35229319; DOI 10.1111/cod.14089
  2. Formaldehyde donors: Human health tier II assessment. Australian Industrial Chemicals Introduction Scheme (2020) · safety assessment
  3. FDA Authority Over Cosmetics: How Cosmetics Are Not FDA-Approved, but Are FDA-Regulated. U.S. Food and Drug Administration (2013) · government guidance · Page updated August 3, 2013; accessed October 1, 2026

Revision history

  1. Initial AI-assisted evidence compilation with source-linked claims, formulation distinctions and explicit research limitations; not independent medical review.