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Dimethicone

Dimethicone in skincare: Emollient, film former, skin protectant. What it does on skin, how strong the evidence behind the claim actually is, the concentrations in normal use, who reacts to it, and where it stands in pregnancy and sunlight. On a label it appears as Dimethicone, Cyclopentasiloxane, Dimethicone Crosspolymer.

Hydration, emollients and barrier repairEmollient, film former, skin protectantEvidence: Strong

On the label: Dimethicone, Cyclopentasiloxane, Dimethicone Crosspolymer. Also called: Silicone, polydimethylsiloxane, PDMS.

This is an ingredient reference, not a diagnosis and not a treatment plan. It describes what substances are and what the published evidence supports; it does not tell you what your skin has or what to put on it. A rash that spreads, hurts, weeps, does not settle, or comes with feeling unwell is a reason to see a doctor or pharmacist, not to change serum.

What it is

A synthetic polymer built on a silicon-oxygen backbone rather than a carbon one. Its chain length determines everything about it: short chains are volatile liquids that flash off and leave a dry finish, long chains are the thick, silky fluids in primers and hair serums. It is chemically inert, does not oxidise, and is used across cosmetics, medical devices and food processing.

What it does on skin

It forms a thin, flexible, water-repellent film that fills surface irregularities. That is why it makes skin feel instantly smooth, why it makes a primer work, and why it stops split ends catching on each other. The film slows water loss without being as occlusive as petrolatum, and it protects skin from friction and moisture — the reason it appears in barrier creams for hands and nappy areas.

What the evidence is worth

Evidence: Strong

Strong as an emollient, film former and skin protectant. Its most interesting evidence is in scarring: silicone gel and silicone sheeting have a genuine place in the management of raised and keloid scars and appear in clinical scar-management guidance. That is silicone doing something real, and it is not the same claim as a primer smoothing your pores.

How it is used

In moisturisers, primers, sunscreens and hair products. As a barrier cream on hands that are washed constantly. As a gel or sheet on a healed raised scar, applied consistently for months, which is the protocol that has evidence behind it — not a week of hopeful dabbing.

Typical concentration in normal use: 1-30% depending on the product. That is a description of the market, not a recommendation, and it is not a dose.

Who reacts to it

Among the least irritating and least allergenic ingredients in use, which is why it dominates products for sensitive and post-procedure skin. Complaints are almost entirely about feel and about pilling when layered under or over incompatible products.

Pregnancy and breastfeeding

Generally considered fine

No pregnancy concerns.

Sunlight

No change

No effect on light sensitivity. Silicones are common in sunscreen bases because they hold the filters in an even film, which improves how well the product actually protects.

Rules and labelling

Dimethicone itself is not restricted. The regulatory action concerns the cyclic silicones — cyclotetrasiloxane, cyclopentasiloxane and cyclohexasiloxane, labelled D4, D5 and D6 — which are restricted in the EU under chemicals law for environmental persistence, first in wash-off cosmetics and with further restrictions extending to leave-on products. That is an environmental measure, not a finding of harm to skin.

What it goes with, and what it does not

Works over a humectant serum and under makeup. Silicone-heavy layers and water-heavy layers applied in the wrong order are the usual cause of pilling, which is a formulation clash rather than a fault in either product.

One thing people get wrong

The myth is that silicones suffocate skin and build up in pores. Dimethicone films are permeable to water vapour, are not occlusive in the way petrolatum is, and come off with ordinary surfactant cleansing. It is non-comedogenic in testing. The legitimate criticism of silicones is environmental, and it applies specifically to the volatile cyclic ones, not to dimethicone.

Sources: EU Cosmetics Regulation (EC) No 1223/2009 and its annexes, as published in the European Commission's CosIng database, for every statement about what is permitted, restricted or banned · opinions of the Scientific Committee on Consumer Safety (SCCS) and safety assessments of the Cosmetic Ingredient Review (CIR) for the concentration positions · standard dermatology reference material for mechanism, tolerability and contact-allergy patterns · checked 2026-09-06. Deep links are deliberately omitted where a stable public URL could not be confirmed.

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