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Moumoujus

IMIDAZOLIDINYL UREA.

Avoid CAS 39236-46-9 / PRESERVATIVE

Imidazolidinyl Urea is a widely utilized formaldehyde-releasing preservative that inhibits a broad spectrum of microbial growth, thereby enhancing product stability and shelf life, with additional minor humectant properties. While regulatory bodies approve its use up to 0.6%, its classification as a formaldehyde donor and high potential for irritation and contact sensitization warrant careful consideration.

Summary

preservative antimicrobial humectant

Science

Mechanism of Action

Imidazolidinyl Urea primarily functions as an antimicrobial preservative by slowly releasing small, controlled amounts of formaldehyde. This mechanism effectively inhibits the growth of a broad spectrum of microorganisms, including bacteria, fungi, and yeast, thereby protecting product integrity and extending shelf life. It also contributes to product stability by preventing active ingredient degradation and offers mild humectant properties to support skin hydration.

Research

Clinical Evidence

Medium confidence
Effective range 0.2–0.6%
Optimal

N/A

Key findings

  1. 01 Demonstrated effective antimicrobial preservative action.
  2. 02 Showed no evidence of primary irritation or allergic contact sensitization in a night cream tested with a repeat insult patch test on eight human subjects.

Transparency

Dusting Analysis

Not commonly dusted

As an antimicrobial preservative, Imidazolidinyl Urea is typically incorporated at functional concentrations (e.g., 0.2-0.6%) essential for product stability and microbial protection, rather than for marketing 'dusting'.

The Formula

Formulation

Solubility
Water
Optimal pH 3 – 9
0 7 14

Stability

This ingredient exhibits optimal stability within an acidic to neutral pH range of 3-9. Its degradation is accelerated under strong alkaline conditions (pH > 9) and by elevated temperatures, with prolonged exposure above 50°C to be avoided. Formaldehyde and nitrosamine release can occur at temperatures exceeding 10°C.

Conflicts

  • Dibenzoil methane derivatives (common UV-A filters)
  • Strongly alkaline environments (pH > 9), which accelerate degradation
  • Nitrites in formulations, particularly in the presence of secondary amines, surfactants, or under elevated temperatures (>35°C), due to the risk of nitrosamine formation.

Safety

Safety Profile

CIR Status
Safe as used
Max tested
0.6%
Sensitization risk High

The Cosmetic Ingredient Review (CIR) Expert Panel has repeatedly affirmed Imidazolidinyl Urea as safe for cosmetic use at concentrations consistent with market practices, with their latest review in 2019. It is approved by global regulatory bodies such as the FDA and the European Commission, which sets a maximum permitted concentration of 0.6% in finished products. A key consideration is its mechanism of action, involving the release of small quantities of formaldehyde. While formaldehyde is recognized as a potential irritant and carcinogen, these released amounts are generally considered within safe limits at the approved usage concentrations. However, studies indicate that concentrations above 1.9% are associated with a notable incidence of contact allergy, and it has been shown to induce hemoglobin release from red blood cells at the maximum authorized concentration (0.6%) after 120 minutes of incubation.

Your Skin

Skin Compatibility

No Normal
No Dry
No Oily
No Sensitive
Irritancy High
Comedogenicity Unknown

Our Assessment

Verdict

Avoid

Given its status as a formaldehyde-releasing agent, high irritancy potential, and documented risk of contact allergy, Imidazolidinyl Urea is generally recommended to be avoided in precision skincare formulations, despite its efficacy as a preservative at concentrations up to 0.6%.

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