Red flag
Evidence key Strong Moderate Weak How we grade
Banned in EU cosmetics Skin allergen Suspected reproductive toxicant Chemical of concern
- 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
- 4080-31-3, 51229-78-8
Why it’s flagged
Prohibited in cosmetics in the EU.
- Annex II entry 1385. Source: EU Cosmetics Regulation, Annex II (prohibited)
- Annex II entry 1386. Source: EU Cosmetics Regulation, Annex II (prohibited)
Annex II of the EU Cosmetics Regulation lists substances that must not be used in cosmetics sold in the EU.
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.
Classified as suspected of damaging fertility or the unborn child.
- EU classification Repr. 2. Source: EU CLP Regulation, Annex VI harmonized classification
EU Repr. 2: suspected of damaging fertility or the unborn child.
Listed as a chemical of concern by the Campaign for Safe Cosmetics.
- “Formaldehyde and formaldehyde-releasing preservatives”. Source: Campaign for Safe Cosmetics
- “Quaternary ammonium compounds”. Source: Campaign for Safe Cosmetics
The Campaign for Safe Cosmetics is an advocacy group. Its profiles explain why it considers these ingredients a concern.
What the research says
We have no graded research on Quaternium-15 by name yet. About ingredients flagged like this one:
- The EU bans more than 1,400 substances from cosmetics, while US rules restrict only a handful. Moderate evidence. Alblooshi 2025
- 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.