High concernEmollient / silicone
Cyclotetrasiloxane
Environmental persistenceReproductive toxicant
What it is
A cyclic siloxane with four silicon-oxygen units, volatile clear liquid.
What it does
Solvent, carrier, and volatile skin-feel modifier.
Why it’s a concern
Classified as PBT (persistent, bioaccumulative, toxic) and vPvB under REACH, and as a reproductive toxicant category 2 in the EU CLP regulation. The EU limits D4 in any cosmetic product above 0.1% from 2020. Leaches from silicone cookware and cosmetics into food and water systems.
Also known as
D4octamethylcyclotetrasiloxane
CAS numbers
556-67-2
Commonly found in
hair careantiperspirant
Safer alternatives
- plant-based emollients
- non-silicone hair serums
Related chemical families
Sources
- ECHA SVHC Entry for D4