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Medicine & cosmetic ingredient

Dimeticone (for head lice)

Silicone in pharmacy head lice lotions and sprays that kills lice physically, not as a nerve poison Also on labels as: dimethicone, dimeticone 4%

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What it does

Dimeticone is a silicone. In head lice treatments it works physically rather than as a nerve poison: it coats the lice, and research suggests it stops them getting rid of water, which kills them (the old explanation was suffocation). Because of this physical action, the British Association of Dermatologists says resistance is unlikely to develop. NICE lists dimeticone 4% products among the recommended treatments, alongside wet combing.

The same family of silicones is used in many conditioners for a smoother feel — see silicones.

How it's used for lice

  • Apply to dry hair, covering the whole scalp and all the hair from root to tip, and leave it on for the time stated on the pack (NICE notes this varies by product).
  • Most treatments are applied twice, about 7 days apart, to catch newly hatched lice.
  • Treat everyone with live lice on the same day.

Cautions

  • Flammable on the hair: NICE warns dimeticone products are combustible. In 2018 the MHRA reported cases of serious burns when treated hair was exposed to flames, for example when lighting cigarettes — keep away from naked flames, cigarettes and other sources of ignition during treatment.
  • Check the age on the pack. BAD says wet combing or dimeticone 4% lotion is generally first choice for children aged 6 months to 2 years, in pregnancy and breastfeeding, and for people with asthma or eczema.
  • Don't use lice treatments to prevent lice — the NHS says they can irritate the scalp.

How strong is the evidence?

Evidence: Strong

Licensed medicine or consistent good-quality trials for this use.

Physical treatments such as dimeticone are first-line options in NICE guidance. In a randomised trial published in the BMJ (2005), 4% dimeticone lotion worked about as well as an older insecticide (phenothrin) and caused fewer irritant reactions; a 2015 BMJ Clinical Evidence review rated dimeticone as likely more effective than malathion or permethrin (moderate-quality evidence).

UK rules and availability

Head lice lotions and sprays can be bought from pharmacies, supermarkets or online (NHS). Check the pack to see whether it's suitable for the person's age, and how to use it.

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. NHS – Head lice and nits nhs.uk
  2. British Association of Dermatologists – Head lice bad.org.uk
  3. NICE CKS – Head lice: management cks.nice.org.uk
  4. emc – Hedrin 4% cutaneous solution (SmPC) medicines.org.uk
  5. Burgess IF. The mode of action of dimeticone 4% lotion against head lice. BMC Pharmacol 2009 pubmed.ncbi.nlm.nih.gov
  6. Burgess IF et al. Treatment of head louse infestation with 4% dimeticone lotion. BMJ 2005 pubmed.ncbi.nlm.nih.gov
  7. Burgess IF. Head lice. BMJ Clin Evid 2015 pmc.ncbi.nlm.nih.gov
  8. MHRA Drug Safety Update – Head lice eradication products: risk of serious burns gov.uk