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Dimethicone

Silicone oil

Well toleratedSiliconeemollientskin conditioningfilm-formeranti-foaming

No meaningful concern for most people; irritation is possible but rare.

Also written as: Polydimethylsiloxane · PDMS · Dimeticone

What it is

Dimethicone is a synthetic silicone polymer built from repeating silicon-oxygen units, made from silica (sand) rather than petroleum. Its molecules are too large to pass through the outer layer of skin, so it stays on the surface. Formulators use it because it spreads easily, cancels the greasy feel of oils, and forms a thin flexible film that slows water loss without feeling heavy.

How it shows up on a label

In face masks it is usually well down the ingredient list, giving the cream or sheet essence its slip and preventing it from feeling tacky as it dries.

What it does well

  • Reduces water loss from the skin surface without truly sealing it

    In a controlled comparison of silicone-based and silicone-free emulsions, the silicone versions produced transepidermal water loss values comparable to untreated control skin, meaning they smooth and protect without behaving like an occlusive wax.

    Moderate evidence

  • Improves texture and reduces the greasy feel of rich formulas

    In the same in vivo comparison, volunteers scored the silicone-containing emulsions higher for silkiness, freshness and softness and lower for greasiness, with no irritation recorded.

    Strong evidence

  • Does not clog pores in the way the popular claim suggests

    The idea that silicones 'suffocate' skin or trap debris in pores is not supported by testing: dimethicone is chemically inert, is not metabolised by skin bacteria, and silicone emulsions did not produce occlusion in vivo. Comedogenicity data that circulate online often come from the rabbit-ear assay, which is known to over-predict reactions in human skin.

    Moderate evidence

Worth knowing

  • Can feel like build-up if a product is not properly cleansed off

    Dimethicone is water-repellent, so a light cleanser may leave a residue that feels slick. A normal surfactant cleanser removes it; this is a texture issue, not a safety one.

    Matters most toPeople who use very rich silicone-heavy products and only rinse with water.

Where the EU stands

No specific restriction

Dimethicone itself is not restricted in EU cosmetics. The cyclic siloxanes D4, D5 and D6 that can occur as residues in silicone raw materials must each stay below 0.1% under REACH Annex XVII entry 70: since 31 January 2020 for D4 and D5 in wash-off cosmetics, and from 6 June 2027 for all other cosmetic products, including leave-on products such as masks.

Regulation (EC) No 1223/2009 - no annex entry for dimethicone, which Annex VI entries 27a and 30a name only as a permitted coating on titanium dioxide (nano) and zinc oxide (nano); the D4/D5/D6 residue limit sits in REACH Annex XVII entry 70, not in this Regulation · source ↗

Sources (2)

Every link goes to the original: a journal, a PubMed record or an EU document.

  1. [1]
    A comparison between silicone-free and silicone-based emulsions: Technological features and in vivo evaluation

    International Journal of Cosmetic Science · 2022 · doi:10.1111/ics.12800

    Silicone-based emulsions were stable, non-irritating and did not cause skin occlusion, with transepidermal water loss comparable to control skin.

  2. [2]
    Analysis of comedone, sebum and porphyrin on the face and body for comedogenicity assay

    Skin Research and Technology · 2016 · doi:10.1111/srt.12244

    Human facial and back testing gives more reliable comedogenicity results than the rabbit-ear model, which over-reacts to materials that do not cause comedones in people.

Masks that contain Dimethicone