What it is
A cyclic siloxane with five silicon-oxygen units, a clear volatile liquid.
What it does
Solvent and carrier that evaporates to leave a silky finish on skin and hair.
Why it’s a concern
D5 is classified by ECHA as very persistent and very bioaccumulative (vPvB) under REACH. The EU restricts D5 in rinse-off products above 0.1% from 2020 and D4/D5/D6 in leave-on above 0.1% from 2027. Accumulation in fish and aquatic sediments is well documented.
Also known as
D5decamethylcyclopentasiloxane
CAS numbers
541-02-6
Commonly found in
hair serumantiperspirantprimer
Safer alternatives
- plant oils
- fatty esters (caprylic/capric triglyceride)
Related chemical families
Sources
- ECHA REACH Annex XVII Entry 70