What is it?
A silicone used in thousands of personal care products. Dimethicone is a synthetic polymer, a chain of alternating silicon and oxygen atoms with methyl groups attached, supplied as a fluid that ranges from thin to very thick. It gives lotions, foundations, primers and conditioners a smooth, silky feel, helps them spread and leaves a light protective film on skin and hair. It is also an over-the-counter skin protectant and a food additive (E900) that controls foaming.
Key information
- The CIR Expert Panel concluded in 2022 that dimethicone is safe as used in cosmetics when formulated to be non-irritating, with data insufficient only for airbrush application.
- Dimethicone is a large linear polymer and penetrates skin very poorly.
- The silicones restricted in the EU for environmental reasons are the small ring-shaped siloxanes D4, D5 and D6, not dimethicone itself.
- Dimethicone can contain traces of those rings; EU law limits each to under 0.1 percent in cosmetics, fully in force from June 2027.
More information
Dimethicone is a mixture of linear siloxane polymers. It is made by polymerizing smaller silicone building blocks, a process that also produces small ring-shaped (cyclic) siloxanes, and traces of these can remain in the finished fluid. Most regulatory concern about silicones is about three of those rings, D4, D5 and D6 (see our Siloxane profile), which are also used as ingredients in their own right.
The Cosmetic Ingredient Review (CIR) Expert Panel reviewed dimethicone in 2003 and again in a 2022 amended report on 30 related polymers. It concluded they are safe as used when formulated to be non-irritating, but that the data were insufficient for products applied with airbrush devices. Dimethicone was reported in 7,747 products, at up to 85 percent. It penetrated human skin very slowly in laboratory tests and was not a skin sensitizer in animal studies or human patch tests. The FDA allows it at 1 to 30 percent as the active ingredient in over-the-counter skin protectants, and in 2020 the European Food Safety Authority found no safety concern for it as a food additive.
In 2018 the EU's chemicals agency identified D4, D5 and D6 as very persistent and very bioaccumulative. EU law now bars each at 0.1 percent or more in cosmetics: since 2020 for D4 and D5 in wash-off products, and after June 6, 2027 for all other cosmetic uses. Dimethicone itself is not restricted. A review by ECETOC, a scientific body whose members are chemical companies, found that dimethicone is expected to be almost entirely removed in sewage treatment, breaks down slowly in soil and, because of its size, is very unlikely to build up in living things.
Reality check: dimethicone is not one of the cyclic siloxanes behind most silicone warnings. Those appear on labels as cyclotetrasiloxane, cyclopentasiloxane, cyclohexasiloxane or cyclomethicone.
Sources: Cosmetic Ingredient Review: Amended safety assessment of dimethicone, methicone, and substituted-methicone polymers as used in cosmetics (2022); EUR-Lex: Commission Regulation (EU) 2024/1328 restricting D4, D5 and D6 under REACH; EFSA Journal (2020): Re-evaluation of dimethyl polysiloxane (E 900) as a food additive; ECETOC: JACC Report 55, Linear polydimethylsiloxanes, second edition (2011)
