Red flag
Evidence key Strong Moderate Weak How we grade
Banned in EU cosmetics Cancer classification Suspected reproductive toxicant
- What it can be used for
- Dissolves other ingredients (the functions the EU ingredient database, CosIng, lists for it; a product may use it for any of them)
- CAS number
- 100-42-5
Why it’s flagged
Prohibited in cosmetics in the EU.
- Annex II entry 1575. 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 known or probable human carcinogen.
- IARC Group 2A (probably carcinogenic to humans). Source: IARC Monographs list of classifications
IARC Group 1 means carcinogenic to humans, Group 2A probably carcinogenic. EU Carc. 1A means known, 1B presumed to cause cancer in humans. These describe a hazard, not the risk at the amount in one product.
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.
What the research says
We have no graded research on Styrene 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
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.