- What it can be used for
- Kills or slows microbes and preserves the product (the functions the EU ingredient database, CosIng, lists for it; a product may use it for any of them)
- CAS number
- 100-97-0
Why it’s flagged
Formaldehyde-releasing preservative.
- EU rules require the label warning “releases formaldehyde” above a set level. Source: EU Regulation 2022/1181 (formaldehyde releasers)
These preservatives slowly release formaldehyde into the product. The EU classifies formaldehyde as a carcinogen and a skin sensitizer, and requires a “releases formaldehyde” warning above a set level.
Classified as a skin sensitizer (may cause an allergic skin reaction).
- Skin Sens. 1 (H317). Source: EU CLP Regulation, Annex VI harmonized classification
EU hazard statement H317: may cause an allergic skin reaction.
What the research says
We have no graded research on Methenamine by name yet. About ingredients flagged like this one:
- In a survey of 187 US pediatric personal-care products, preservatives (57.8% of products) were a more common source of contact allergens than fragrance (29.4%), even though the products were being screened specifically for hypoallergenic/fragrance-related marketing claims. Moderate evidence. Hamann 2015
Each finding shows its evidence grade. See every graded fact or how we grade.
What this page can’t tell you
These lists describe what a substance can do, its hazard. The risk from one product depends on how much is in it and how you use it, and the label doesn’t say how much.
Not being on a list doesn’t make an ingredient safe. It may never have been assessed.
Check your products
Check a whole labelProducts that list itEWG Skin DeepShop fragrance-free
“Products that list it” opens Open Beauty Facts, a free database anyone can edit.
Flagged the same way
Official lists checked September 2026. Spotted a mistake? Tell us.