Cyclopentasiloxane
D5 · Cyclomethicone 5
What it is
A cyclic volatile silicone (decamethylcyclopentasiloxane, D5) used as an emollient, spreading agent, and carrier that evaporates after application.
In this product: Emollient carrier, gives the stick its smooth glide and flash-evaporates.
Dose & route, what actually matters
Dermal and environmental. D5 is highly volatile, it evaporates from skin into the atmosphere and reaches aquatic systems via drain. The restriction is driven by aquatic persistence (PBT designation), not dermal toxicity.
EUROPEAN UNION
Restricted to ≤0.1% in rinse-off cosmetics since January 2020 (Regulation (EU) 2018/35). Commission Regulation (EU) 2024/1328 extends the ≤0.1% limit to ALL cosmetic products including leave-on (antiperspirant sticks), with compliance deadline June 6, 2027.
UNITED STATES
No restriction on D5 in antiperspirants or leave-on cosmetics. Products remain legal at current formulation concentrations indefinitely.
The evidence
SCCS Opinion SCCS/O/174 (2021) concluded D5 is safe for human health in cosmetic products; EU restriction is based on environmental persistence (PBT, Persistent, Bioaccumulative, Toxic to aquatic organisms).
regulatory · 2021 · source
Commission Regulation (EU) 2024/1328 extends D5 restriction to all cosmetic products; leave-on products including antiperspirant sticks must comply by June 6, 2027.
regulatory · 2024 · source
California Prop 65: Not listed.
How to avoid it
EU-market formulations of these products will be reformulated by 2027. In the US, check the INCI list, Cyclopentasiloxane or Cyclomethicone are the names to look for.
Where it hides
Editorial analysis of publicly available regulatory and peer-reviewed sources. Not medical advice. We name our evidence and link it, including when an ingredient is fine.