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Cosmetic ingredient

Silicones

Smoothing, detangling and shine in conditioners, serums and heat protectants Also on labels as: dimethicone, amodimethicone, dimethiconol, cyclomethicone, cyclopentasiloxane

Reviewed on

What it does

Silicones are the most widely used conditioning agents in hair care. Review articles describe them forming a thin film on the hair that reduces friction between strands — so hair tangles less, feels smoother, looks shinier and has less static and frizz. Some reviews also say they may help protect hair from heat and from the abrasion of brushing.

There are a few types you'll see on labels:

  • Dimethicone — the most common. It's water-repellent and sticks better to healthy hair than to damaged ends, so products use other ingredients to help it deposit.
  • Amodimethicone — an "amino" silicone with a positive charge, designed to cling to damaged areas.
  • Cyclic silicones (cyclomethicone, cyclopentasiloxane) — light, evaporating carriers that leave a silky feel.

Cautions

  • Build-up: heavy use of silicone-rich products can leave fine hair feeling weighed down. A clarifying wash now and then sorts this out. We found no peer-reviewed evidence that silicones "suffocate" or damage hair.
  • Environment: some cyclic silicones persist in the environment. In Great Britain, D4 is banned in cosmetics, and D4 and D5 are restricted in wash-off products such as shampoo and conditioner (0.1% limit) under UK REACH.

How strong is the evidence?

Evidence: Cosmetic

Changes how hair looks or feels; not a treatment for any condition.

The benefits — less friction, more shine, easier combing — come from laboratory measurements described in hair-science reviews. A US Cosmetic Ingredient Review panel judged dimethicone and related silicones (including amodimethicone) safe as used in cosmetics, and found dimethicone wasn't absorbed through skin in the studies it reviewed. We found no clinical trial showing silicones harm hair.

UK rules and availability

Dimethicone and amodimethicone are permitted cosmetic ingredients. D4 (octamethylcyclotetrasiloxane) is prohibited in GB cosmetics; D4 and D5 are restricted in wash-off products.

Products on this site that list it

Not medical advice. This guide is general information from the sources listed, not a diagnosis or a substitute for a pharmacist, GP or dermatologist. If you are worried, or symptoms are severe or not improving, get advice. Read our health information policy.

Sources

  1. Gavazzoni Dias MF. Hair cosmetics: an overview. Int J Trichology 2015 pmc.ncbi.nlm.nih.gov
  2. D'Souza P, Rathi SK. Shampoo and conditioners: what a dermatologist should know? Indian J Dermatol 2015 pmc.ncbi.nlm.nih.gov
  3. Cosmetic Ingredient Review – Final report on the safety assessment of dimethicone and related silicones. Int J Toxicol 2003 pubmed.ncbi.nlm.nih.gov
  4. legislation.gov.uk – Cosmetics Regulation Annex II (prohibited substances) legislation.gov.uk
  5. legislation.gov.uk – UK REACH Annex XVII (restrictions) legislation.gov.uk
  6. HSE – UK REACH regulatory management options analysis for D4, D5 and D6 (call for evidence) consultations.hse.gov.uk