Silicones, Explained: Safety, the D4/D5/D6 Rules and the Best Alternatives
Few ingredient families start as many arguments as silicones. Some people love the silky, weightless feel they give. Others avoid them completely. As usual, the truth is more interesting than either side. Let's separate the facts from the hype.
What silicones do
Silicones are synthetic polymers built on a silicon-oxygen backbone. In cosmetics they give:
- Slip and silkiness: that "velvet" glide in primers and serums.
- A breathable protective film that reduces water loss.
- Shine and detangling in hair care.
- Light, non-greasy texture that helps rich formulas feel elegant.
The family
- Dimethicone: the classic linear silicone, from light fluids to thick grades like Dimethicone 350 cSt.
- Dimethicone Crosspolymer: the powdery, blurring "primer feel".
- Amodimethicone: conditions hair, targeting damaged areas.
- Phenyl Trimethicone: high shine for hair and lip gloss.
- Cyclic (volatile) silicones like Cyclopentasiloxane (D5) and Cyclohexasiloxane (D6): they give a dry, evaporating glide. These are the ones facing restrictions (below).
Are they safe for skin?
The US Cosmetic Ingredient Review expert panel concluded that dimethicone and related silicones are safe as used in cosmetics (CIR, International Journal of Toxicology, 2003). A later review restated that dimethicone is generally not absorbed through skin and isn't a sensitiser (CIR, 2017). Dimethicone is even an approved active ingredient in US over-the-counter skin protectants at 1–30% (21 CFR 347.10).
"Do silicones suffocate skin or cause breakouts?" Silicone films are permeable to air and water vapour, so they don't "suffocate" skin. Breakouts usually come down to the whole formula and how well it's cleansed off, not one ingredient family.
Why some silicones are being restricted
The concern is environmental, not skin safety. Some cyclic silicones persist in the environment and can accumulate in living things.
- The EU limited D4 and D5 to below 0.1% in wash-off cosmetics, because D4 is classed as persistent, bioaccumulative and toxic, and D5 as very persistent and very bioaccumulative (Regulation (EU) 2018/35).
- A newer regulation extends the 0.1% limit for D4, D5 and D6 to other cosmetics, applying from 6 June 2027 (Regulation (EU) 2024/1328).
If you sell in the EU, or plan to, reformulate products that rely on D5 or D6 now. Our product pages flag these with a regulatory note (see the cyclopentasiloxane entry).
The best alternatives
Formulators have been actively developing silicone-free options. A Cosmetics & Toiletries overview names light hydrocarbons and esters such as isododecane, isohexadecane, coco-caprylate and dicaprylyl ether (Cosmetics & Toiletries).
- To replace D5's dry, volatile glide: Isododecane or Isohexadecane (both flammable, so handle with care), or Cyclomethicone Substitute (Isoamyl Laurate Blend).
- For a silky, light emollient feel: Coco-Caprylate, Dicaprylyl Carbonate, Dicaprylyl Ether.
- For a skin-friendly, natural-origin glide: Squalane (see our squalane post).
- For hair shine and detangling: conditioning polymers and quats plus light oils can cover a lot, though matching amodimethicone fully is tricky.
Tip: no single alternative copies a silicone exactly. Blending two or three emollients with different spreading speeds usually gets closest.
So, silicone or not?
Linear silicones like dimethicone have a strong safety record on skin. Cyclic D4, D5 and D6 are on their way out in the EU for environmental reasons. And a growing number of customers simply prefer silicone-free. Choose for your market and your brand values, and label honestly.
Explore Silicones & Film Formers, Slip & Sensory Modifiers and Esters & Emollient Bases.