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preservative

Diazolidinyl Urea

Watch if sensitive·Moderate evidence

A formaldehyde-releasing preservative that slowly gives off small amounts of formaldehyde to keep bacteria and mold from growing in the bottle. CIR set a maximum use level of 0.5%, at which released formaldehyde stays under generally accepted skin-safety thresholds, but people with a formaldehyde or fragrance-mix contact allergy sometimes react to it and may want to avoid the ingredient regardless of the low dose.

Worth knowing

  • Known contact sensitizer for some

Gentler alternatives

Questions

Does diazolidinyl urea release formaldehyde?
Yes, diazolidinyl urea slowly releases small amounts of formaldehyde to preserve the product and prevent bacterial growth. Safety assessments set a maximum use level of 0.5%, at which the released formaldehyde stays below generally accepted skin-safety thresholds.
Is diazolidinyl urea safe?
Safety assessments have found diazolidinyl urea acceptable at approved use levels. However, people with a fragrance-mix or formaldehyde contact allergy sometimes react to it and may want to avoid it regardless of the low dose.
What is diazolidinyl urea used for?
Diazolidinyl urea is a preservative that keeps bacteria and mold from growing in cosmetics; it is commonly used in leave-on products like moisturizers and serums.

Products with Diazolidinyl Urea

In our guides

References

Cosmetic information for general education, not medical advice. A verdict is a reading of the published evidence, never a guarantee for your skin: any ingredient can irritate someone, so patch test new products and see a professional if you react. Concern is graded on cited evidence, never on hazard-score lists. See how we score.