Cyclopentasiloxane
AKA “Cyclomethicone 5, Dimethylsiloxane pentamer, Dow corning 345, Cyclic dimethylsiloxane pentamer, NUC silicone VS 7158”
Synthetic
Ingredient Facts
Cyclopentasiloxane
AKA: Cyclomethicone 5, Dimethylsiloxane pentamer, Dow corning 345, Cyclic dimethylsiloxane pentamer, NUC silicone VS 7158
Synthetic · Emollient · EWG: 4
Synthetic
Emollient
Solvent
Skin Conditioner
Hair Care
Silicone
Synthetic
Clean
A lightweight silicone that smooths and conditions hair and skin, leaving a soft, non-greasy finish while helping products spread evenly.
Formula
C10H30O5Si5
Mol. Weight
370.77
CAS #
541-02-6
Form
Liquid
State
Liquid
See origin →
Functions
Hair Conditioning
A catch-all term for ingredients that improve how skin looks and feels — softer, smoother, more supple. The workhorse behind most moisturizers.
Emollient
Fills in the tiny cracks between skin cells to make everything feel smooth and soft. The "silky finish" ingredient.
Solvent
Dissolves other ingredients so they distribute evenly in the formula. Often the invisible "base" everything else is mixed into.
Locks In Moisture
Traditional Use
A cyclic silicone polymer developed in mid-20th century silicone chemistry research. Used in cosmetics as a lightweight volatile carrier and emollient, designed to replace heavier traditional oils and waxes.
Skin Types
●all-skin-types
Best For
General
Melanin-Rich Skin
Suitable
Pregnancy & Breastfeeding Safe
Yes
EWG
4
CIR
Safe w/Qualifications
Pregnancy
Yes
Restricted By
CIR Safety Findings
medical-approval
all-shades-safe
Regulatory Agencies
Safety assessment of Cyclomethicone, Cyclotetrasiloxane, Cyclopentasiloxane, Cyclohexasiloxane and Cycloheptasiloxane
Cosmetic Ingredient Review (CIR) Expert Panel
International Journal of Toxicology
Cyclopentasiloxane
European Commission
EU Cosmetic Ingredient Database (CosIng)
Cyclopentasiloxane
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
Safety assessment of cyclomethicone, cyclotetrasiloxane, cyclopentasiloxane, cyclohexasiloxane, and cycloheptasiloxane.
Johnson W Jr, Bergfeld WF, Belsito DV, Hill RA, Klaassen CD et al.
International journal of toxicology, 2011
Safety assessment of cyclomethicone, cyclotetrasiloxane, cyclopentasiloxane, cyclohexasiloxane, and cycloheptasiloxane.
Johnson W Jr, Bergfeld WF, Belsito DV, Hill RA, Klaassen CD et al.
International journal of toxicology, 2011
Safety assessment of cyclomethicone, cyclotetrasiloxane, cyclopentasiloxane, cyclohexasiloxane, and cycloheptasiloxane.
Johnson W Jr, Bergfeld WF, Belsito DV, Hill RA, Klaassen CD et al.
International journal of toxicology, 2011
Verified Feb 2026
Data: PubChem · CosIng · EWG · CIR