- What it can be used for
- Forms a film on skin or hair (the functions the EU ingredient database, CosIng, lists for it; a product may use it for any of them)
- CAS number
- 9003-53-6
Why it’s flagged
Listed as a chemical of concern by the Campaign for Safe Cosmetics.
- “Styrene”. 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
- In a lab-grown 3D model of human skin, polystyrene fragments up to 10 µm were cytotoxic and inflammatory in keratinocytes, but only the fragments 2 µm or smaller penetrated into the dermis (average maximum 4.7 µg) within an hour, switching on inflammation genes there. Weak evidence. Han & Kim 2025
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.