Ingredient review
Imidazolidinyl Urea
INCI: Imidazolidinyl Urea
A common, effective preservative that helps keep your products fresh, but may release trace formaldehyde and can be a mild irritant for sensitive skin.
In plain English
Imidazolidinyl urea is a synthetic preservative added to many water-based cosmetics to stop bacteria, yeast, and mold from growing. It works by slowly releasing a tiny amount of formaldehyde, which kills germs. This ingredient has been used for decades and is considered safe at low levels, but some people with very sensitive skin may experience mild irritation. It is not a moisturizer or active treatment—it's there to protect the product, not your skin.
Review score
Safety, usefulness, and evidence
Potentially useful with some tradeoffs
The evidence base is relatively strong for its common cosmetic role.
Risk flags are low for most users, though the finished product can still irritate.
- Source
- synthetic
- Evidence
- strong
- Irritation
- low
- Clogging risk
- low
Quick decision guide
Useful, but context matters
Imidazolidinyl Urea is generally a lower-concern ingredient when the full formula suits your skin.
Plain-English read
Treat this as a practical screening step before you compare products that contain this ingredient.
- Step 1Start with the score, then check the irritation and clogging risk before judging Imidazolidinyl Urea.
- Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
- Step 3If a product stings, breaks you out, or worsens irritation, judge the finished formula and stop using it even if the ingredient scores well.
Score terms in plain English
Irritation risk
lowLess likely to sting, burn, or bother most users, though sensitive skin can still react.
Clogging risk
lowLess likely to feel heavy or contribute to clogged pores for most skin types.
Evidence level
strongThere is a stronger practical or research basis for the ingredient role described here.
What it is
A white, odorless powder that is a formaldehyde-releasing preservative, commonly used in rinse-off and leave-on cosmetics.
How it works
It slowly releases small amounts of formaldehyde over time, which prevents the growth of microorganisms in the product. This extends the shelf life and keeps the formula safe to use.
Pros
Effective preservation
Stops a wide range of microbes, keeping your products safe and fresh for longer.
Well-studied safety
Extensively tested and approved by regulators worldwide at typical use levels.
Cons and cautions
Formaldehyde release
Releases trace amounts of formaldehyde, which can be a concern for those with allergies or sensitivities.
Potential irritation
May cause mild stinging or redness in people with very reactive skin, especially in leave-on products.
Best for
- People using conventional water-based cosmetics
- Those who want affordable, well-tested preservation
Use caution if
- Individuals with known formaldehyde allergy or very sensitive skin
Usage tips
Safety summary
Considered safe for most people at typical cosmetic levels. The formaldehyde release is very low (below 0.1% free formaldehyde), but individuals with a known formaldehyde allergy should avoid it. Mild irritation is possible for sensitive skin.
Research notes
Multiple safety reviews by the Cosmetic Ingredient Review (CIR) panel and the SCCS (EU) confirm its safety at concentrations up to 0.6%. Studies show it is an effective preservative with a low irritation profile for the general population.
Common label clues
- Typical concentration
- 0.1% to 0.5%
- Regulatory status
- Approved by the FDA, EU CosIng, and other global regulators for use in cosmetics at concentrations up to 0.6%.
- Common uses
- Moisturizers, Shampoos, Conditioners, Body washes, Sunscreens
- Environmental note
- Synthetic ingredient; not biodegradable. May contribute to microbial resistance if overused in the environment.
Good to know
- Often listed near the end of ingredient lists because it's used at low concentrations.
- Not the same as formaldehyde—it's a preservative that releases a tiny amount over time.
Common questions
What is Imidazolidinyl Urea in beauty products?
Imidazolidinyl urea is a synthetic preservative added to many water-based cosmetics to stop bacteria, yeast, and mold from growing. It works by slowly releasing a tiny amount of formaldehyde, which kills germs. This ingredient has been used for decades and is considered safe at low levels, but some people with very sensitive skin may experience mild irritation. It is not a moisturizer or active treatment—it's there to protect the product, not your skin.
What does Imidazolidinyl Urea do in a beauty product?
It slowly releases small amounts of formaldehyde over time, which prevents the growth of microorganisms in the product. This extends the shelf life and keeps the formula safe to use.
Is Imidazolidinyl Urea safe for most people?
Considered safe for most people at typical cosmetic levels. The formaldehyde release is very low (below 0.1% free formaldehyde), but individuals with a known formaldehyde allergy should avoid it. Mild irritation is possible for sensitive skin.
Who should be careful with Imidazolidinyl Urea?
Individuals with known formaldehyde allergy or very sensitive skin
Research sources
Ingredient reviews are educational and are not medical advice. Patch test new products and ask a licensed clinician about persistent irritation, allergies, pregnancy-specific questions, or diagnosed skin conditions.