--- title: "Cyclopentasiloxane" description: "Cyclopentasiloxane (D5) is a volatile cyclic silicone used for spread and light feel; EU cosmetic limits address environmental release." --- # Cyclopentasiloxane > Cyclopentasiloxane (D5) is a volatile cyclic silicone used for spread and light feel; EU cosmetic limits address environmental release. Source: https://cosmetic-labs.com/glossary/cyclopentasiloxane Created: 2026-11-09T14:47:14+00:00 Modified: 2026-11-09T14:47:14+00:00 Author: Emilie SCHOL ## Definition of Cyclopentasiloxane Cyclopentasiloxane, also called D5, is a cyclic silicone used in cosmetics as a solvent and skin- or hair-conditioning ingredient. It spreads easily and evaporates from the surface, giving formulations a light feel; EU limits on D5 also address environmental persistence. ### Learn more ## What D5 means Cyclopentasiloxane is also known as decamethylcyclopentasiloxane or D5. It is a cyclic silicone ingredient, rather than a general synonym for every silicone or every cyclomethicone mixture. Cosmetic ingredient information lists solvent, skin-conditioning, [emollient](https://cosmetic-labs.com/glossary/emollient), and hair-conditioning roles. These labels describe possible uses in formulas, not a guaranteed outcome from any product containing D5. As a solvent and spreading aid, D5 can affect how other ingredients are distributed in a formulation. It is used in hair and skin products where a light sensory profile is desirable. Its role depends on the rest of the recipe: the presence of a silicone on a label cannot reveal the product’s full composition, deposition behavior, or measured conditioning result. ## Why it feels light D5 is a volatile silicone: it can evaporate from skin or hair after application. Volatility describes evaporation, not skin irritation. This can let a formula spread smoothly without leaving the same heavy feel as a less volatile liquid. The remaining ingredients can still leave a film or alter how the final product feels. Formulators distinguish the transient behavior of D5 from the performance of the complete product after application. A serum can contain D5 alongside oils, polymers, or other silicones. Those materials may remain after D5 evaporates. Claims about a finished product’s softness, shine, or long-term behavior should be supported by evaluation of that product rather than extrapolated from one volatile ingredient. ## Environmental and regulatory context D5 has drawn regulatory attention as a very persistent and very bioaccumulative substance. EU REACH rules already restrict D5 at or above 0.1% by weight in wash-off cosmetic products. An amended restriction applies that concentration threshold to cosmetic products other than wash-off products after 6 June 2027. The timing and jurisdiction matter: as of November 2026, the later leave-on date has not yet arrived. The EU measure is concerned with environmental releases; it should not be rewritten as proof that topical D5 in any particular cosmetic causes a medical condition. It also is not a worldwide prohibition. Formulators assessing a market need to check the applicable rules, product category, timing, and full legal text rather than assuming every formulation has the same compliance status. ## Reading an ingredient list A D5 listing indicates the ingredient may help with solvent behavior, spread, and conditioning feel. It does not specify concentration or establish that a product is clinically effective. The precise distinction between ingredient function, finished-formula results, and environmental regulation keeps three different questions from being collapsed into one. Someone comparing products can treat D5 as a clue about a possible lightweight, spreading texture while still judging the formula as a whole. For developers, its functional advantages and applicable regulatory deadlines must both be considered. Neither an ingredient’s historic use nor a regulator’s environmental concern is, by itself, a performance test of a specific cosmetic. Sources ## Sources and references References supporting this page are listed below. Source access dates and supported claims are recorded in the evidence notes where available. [European Commission CosIng: cyclopentasiloxane](https://ec.europa.eu/growth/tools-databases/cosing/details/75413) URL [https://ec.europa.eu/growth/tools-databases/cosing/details/75413](https://ec.europa.eu/growth/tools-databases/cosing/details/75413) [SCCS opinion on D5 in cosmetic products](https://health.ec.europa.eu/document/download/5d0306e6-1853-4cfc-b351-e5908684eb0f_en) URL [https://health.ec.europa.eu/document/download/5d0306e6-1853-4cfc-b351-e5908684eb0f_en](https://health.ec.europa.eu/document/download/5d0306e6-1853-4cfc-b351-e5908684eb0f_en) [SCCS opinion on D5 in cosmetic products](https://health.ec.europa.eu/document/download/5d0306e6-1853-4cfc-b351-e5908684eb0f_en) URL [https://health.ec.europa.eu/document/download/5d0306e6-1853-4cfc-b351-e5908684eb0f_en](https://health.ec.europa.eu/document/download/5d0306e6-1853-4cfc-b351-e5908684eb0f_en) [Commission Regulation (EU) 2024/1328](https://eur-lex.europa.eu/eli/reg/2024/1328/oj) URL [https://eur-lex.europa.eu/eli/reg/2024/1328/oj](https://eur-lex.europa.eu/eli/reg/2024/1328/oj) [Commission Regulation (EU) 2024/1328](https://eur-lex.europa.eu/eli/reg/2024/1328/oj) URL [https://eur-lex.europa.eu/eli/reg/2024/1328/oj](https://eur-lex.europa.eu/eli/reg/2024/1328/oj) [Commission Regulation (EU) 2024/1328](https://eur-lex.europa.eu/eli/reg/2024/1328/oj) URL [https://eur-lex.europa.eu/eli/reg/2024/1328/oj](https://eur-lex.europa.eu/eli/reg/2024/1328/oj) [Commission Regulation (EU) 2024/1328](https://eur-lex.europa.eu/eli/reg/2024/1328/oj) URL [https://eur-lex.europa.eu/eli/reg/2024/1328/oj](https://eur-lex.europa.eu/eli/reg/2024/1328/oj) --- ## Site identity - Organization: Cosmetic Labs - Description: Cosmetic Labs is a directory and a platform to meet all your cosmetic product development needs. From sourcing raw material to finding the best CRO for your needs. - Website: https://cosmetic-labs.com