Is cyclopentasiloxane banned? D5 rules in the EU, Canada and US
Cyclopentasiloxane (D5) is not banned outright. The EU restricts it at 0.1% or more in wash-off cosmetics, and in leave-on products after 6 June 2027.
Cyclopentasiloxane (D5) and its regulatory status
Cyclopentasiloxane is decamethylcyclopentasiloxane, the cyclic silicone called D5 (CAS 541-02-6), used in cosmetics and personal care. It is not banned outright in the EU, Canada or the United States. REACH Annex XVII entry 70 restricts placing it on the market at 0.1% by weight or more: wash-off cosmetics after 31 January 2020, and leave-on cosmetics after 6 June 2027. Canada decided in 2012 that D5 is not toxic under CEPA, and the US FDA doesn't restrict it in cosmetics.
What is cyclopentasiloxane?
Cyclopentasiloxane is a volatile silicone, used in cosmetics for a light, silky feel that does not stay greasy. D5 is assessed with two other cyclic siloxanes: D4, octamethylcyclotetrasiloxane (cyclotetrasiloxane, CAS 556-67-2), and D6, dodecamethylcyclohexasiloxane (cyclohexasiloxane, CAS 540-97-6). Cyclomethicone (CAS 69430-24-6) is a mixture made mostly of D4, D5 and D6. Canada's December 2023 Siloxanes Group assessment leaves cyclomethicone out of further Chemicals Management Plan work for now, because the D4, D5 and D6 assessments already cover it. The names are not interchangeable.
Is cyclopentasiloxane banned in the EU?
No. Regulation (EU) 2018/35 first restricted D4 and D5 in wash-off cosmetics. Regulation (EU) 2024/1328 replaced entry 70, added D6 and extended the rule. Placing on the market is restricted at a concentration equal to or greater than 0.1% by weight of the respective substance:
| Use | Restricted after |
|---|---|
| D4 and D5 in wash-off cosmetics | 31 January 2020 |
| D4, D5 and D6 on their own, as constituents of other substances, or in mixtures (general rule) | 6 June 2026 |
| Other cosmetics, including leave-on products and D6 in wash-off products | 6 June 2027 |
| Medical devices, in vitro diagnostics, and medicinal and veterinary medicinal products | 6 June 2031 |
Entry 70 also derogates specified industrial uses, some scar, wound and stoma care devices, and these substances as constituents of a silicone polymer.
Wash-off means a cosmetic that, under normal conditions of use, is washed off with water after application. D5 as a dry cleaning solvent is restricted after 6 June 2034, with strictly controlled closed systems exempt.
D4 is already prohibited in EU cosmetics under Annex II entry 1388. The 2027 leave-on date does not reopen cosmetics to D4.
Great Britain has not adopted the 2024 extension. UK REACH entry 70 is still the D4 and D5 wash-off rule, at 0.1%, after 31 January 2020. D4, D5 and D6 remain substances of very high concern under UK REACH. HSE's July 2025 technical report recommends no new restriction.
Is cyclopentasiloxane safe? Side effects and cancer claims
In SCCS/1549/15 (adopted 25 March 2015, revised 29 July 2016), the EU Scientific Committee on Consumer Safety considers D5 safe in cosmetic products at the reported concentrations, except in hair styling aerosols and sun care spray products. The opinion does not cover oral care, and it did not assess the environment. D4 impurity should be kept as low as possible.
Health Canada says D4, D5 and D6, the cyclic siloxanes used in cosmetics, "do not present a risk to human health as currently used". The 2018 wash-off restriction addressed D4 and D5 in wastewater, not a finding that cyclopentasiloxane causes cancer.
Canada's D5 decision
The 2009 assessment found a possible harmful effect on the environment, and a low risk to human health. A Board of Review chaired by Prof. John Giesy reported on 20 October 2011 that siloxane D5 does not pose a danger to the environment. The 25 February 2012 decision annulled the 2009 finding: D5 meets none of the criteria in section 64 of CEPA.
D4 was added to CEPA Schedule 1 in 2011. Listing does not restrict its use, manufacture or import, and no personal-care measure was warranted. A D4 industrial effluent notice is in effect, but it does not ban D4 in cosmetics. D6 was not harmful to human health at the exposures assessed, and was not entering the environment at harmful levels. D4, D5, D6 and cyclomethicone are absent from the Cosmetic Ingredient Hotlist.
United States
The FDA list does not include cyclopentasiloxane, cyclomethicone, D4, D5 or D6, and there is no TSCA risk evaluation for D5 or D6. EPA's draft risk evaluation, noticed on 17 September 2025, is about D4. It preliminarily finds unreasonable risk to workers (23 conditions of use), consumers (one) and the environment (seven), not to the general population. EPA's Science Advisory Committee on Chemicals published its final peer review on 12 June 2026. The evaluation was still a draft in October 2026.
RegAffairs AI has a cited answer on cyclopentasiloxane in cosmetics, Canada's D5 decision, and D4 and D6.