Diazolidinyl Urea: What Is It, Cosmetic Uses, Benefits & Side Effects

Curious about this ingredient? In this article we're explaining exactly what it is and why it's used within cosmetic formulations.
Updated on: June 27, 2025
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We verify all information on this page using publicly available nomenclature standards from The Personal Care Products Council (PCPC), the European Commission's CosIng database and documentation provided directly by ingredient manufacturers. Our analysis is based on technical data from these sources to ensure accuracy and reliability.

What Is Diazolidinyl Urea?

Diazolidinyl urea is a synthetic preservative created to keep cosmetics free of harmful microbes. Chemically, it is a formaldehyde releaser built from urea and glyoxal that forms a five-membered imidazolidinyl ring with attached hydroxymethyl groups.

It first appeared in personal care items in the 1970s when formulators searched for alternatives to older, less efficient preservatives. Production involves reacting allantoin or similar urea compounds with formaldehyde under controlled heat and pH, then purifying the result into a white, water-soluble powder. Because it works well in water-based formulas and remains effective across a wide pH range, manufacturers use it in creams, lotions, liquid foundations, shampoos, conditioners, wipes, masks, serums and many anti-aging or daily moisturizers.

Diazolidinyl Urea’s Cosmetic Benefits/Uses

This ingredient serves one main purpose that greatly influences product shelf life and safety. Diazolidinyl urea acts as a preservative, which means it prevents the growth of bacteria, yeast and mold in water-rich cosmetics. By keeping microbes out, it helps maintain product freshness, protects the user from potential infections and allows brands to offer reasonable expiration dates without refrigeration.

Who Can Use Diazolidinyl Urea

Diazolidinyl urea is generally considered suitable for all skin types because it is used at very low levels, usually under 1%. Oily, dry, combination and normal skin can typically tolerate it. Sensitive or compromised skin might react if it is already prone to preservative allergies, so people in that group may prefer formulas that avoid formaldehyde releasers.

The ingredient is synthetically produced from non-animal sources, so products that use it are usually appropriate for vegans and vegetarians. Always check the full ingredient list to be certain no other animal-derived additives are included.

No research shows that diazolidinyl urea poses specific risks to women who are pregnant or breastfeeding when applied topically in cosmetic concentrations. That said, this is not medical advice. Anyone who is pregnant or nursing should review their skincare routine with a qualified healthcare professional before making changes, just to be safe.

Diazolidinyl urea does not increase photosensitivity, so there is no special need for extra sun precautions beyond everyday sunscreen use. The ingredient is also compatible with most other common cosmetic actives and does not interfere with makeup wear or sunscreen performance.

Potential Side Effects/Adverse Reactions

Individual responses to diazolidinyl urea can differ. The points below cover potential side effects, but most users will not experience them when the ingredient is used correctly in a well-formulated product.

  • Mild skin irritation
  • Redness or itching in people sensitive to formaldehyde or formaldehyde releasers
  • Allergic contact dermatitis in rare cases
  • Stinging or burning on broken or freshly exfoliated skin
  • Eye irritation if the product accidentally gets into the eyes

If you notice any of these issues while using a product that contains diazolidinyl urea, stop using the item and consult a healthcare professional for advice.

Comedogenic Rating

Rating: 0/5

Diazolidinyl urea is water soluble and used at very low percentages, so it does not leave an oily film that can block pores. Because it simply dissolves into the water phase of a formula and rinses clean, it shows no tendency to provoke blackheads or whiteheads.

People who are prone to acne or breakouts can generally use products containing diazolidinyl urea without worrying about clogged pores.

The only pore-related concern would come from other ingredients in the same product, not the preservative itself.

Summary

Diazolidinyl urea is a synthetic preservative that keeps creams, lotions, shampoos and other water-rich cosmetics free of bacteria yeast and mold. It works by slowly releasing trace amounts of formaldehyde that disrupt microbial cell walls which gives finished products a longer, safer shelf life.

Its popularity sits in the middle ground: many mainstream brands still rely on it thanks to its broad antimicrobial action and wide pH tolerance, while some natural or sensitive-skin lines skip it in favor of newer preservative systems.

Regulatory panels consider diazolidinyl urea safe in cosmetics at the low levels used, but as with any ingredient it can trigger irritation in a small fraction of users. When trying a new product that contains it, do a quick patch test on a small area first to make sure your skin gets along with the formula.

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