Topical pediculicide (silicone-based) Pregnancy: There is no data to suggest that it may not be used in pregnancy.

Dimeticone

Brand names: Hedrin, Lyclear, Full Marks Solution

Dimeticone is a topical silicone-based preparation used to treat head lice and is also used as a barrier and emollient ingredient on the skin.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Apply sufficient 4% cutaneous solution to cover dry hair from base to tip, ensuring no part of the scalp is left uncovered; work into the hair, spreading evenly from roots to tips

Route: Topical, external use only (applied to dry hair and scalp)

Frequency: Leave on the hair for a minimum of 8 hours or overnight, then wash out with normal shampoo and rinse thoroughly with water; repeat the treatment after seven days

UK SPC (Hedrin 4% cutaneous solution) — head lice. Posology is stated for adults and children aged six months and above; children under six months should only be treated under medical supervision (no per-kg dose is given). Allow hair to dry naturally after application. Consult a pharmacist if live lice are detected after the second treatment or if head lice are persistent or recurring. Flammability: the solution is combustible when on the hair and in direct contact with an open flame or other source of ignition — keep hair away from naked flames and burning cigarettes during treatment; treated hair can readily burn if ignited. Avoid contact with the eyes; if accidentally introduced into the eyes, flush with water. Note: the US label retrieved for cross-check was an incontinence barrier cream (a different indication), so it was not used.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to any of the ingredients

Side effects

Skin irritation
Itchy or flaky scalp
Irritation around the eyes
Hair loss (single cases reported)
Hypersensitivity reactions including rash, urticaria, generalised pruritus and breathing difficulties — shampoo off immediately and seek medical advice if symptoms do not resolve

Interactions

Dimeticone is not known to interact with other drugs

Clinical monograph

How it works

When used for head lice it acts physically rather than chemically, coating the lice and disrupting their ability to manage water and function, leading to their death.

Prescribing in practice

Because it works by a physical mechanism it avoids neurotoxic insecticide resistance, but a second application is usually needed to kill lice that hatch after the first treatment.
Some formulations are flammable, so keep treated hair away from naked flames and sources of ignition while wet.
It is well tolerated and suitable across a wide range of patients, with local scalp irritation being the main adverse effect.

Monitoring

Monitoring is clinical, confirming clearance of live lice after treatment and checking for scalp irritation.

Counselling the patient

Follow the application instructions and repeat the treatment after the recommended interval to catch newly hatched lice.
Keep treated hair away from flames, cigarettes and hairdryers while it is wet, as some products are flammable.
Detection combing helps confirm the lice have gone; report any scalp irritation.

Evidence & guidelines

Physical insecticides such as dimeticone are recommended options for head lice in current prescribing references and NICE guidance, avoiding chemical resistance.

Reference: NICE CKS Head Lice; PHE/UKHSA head lice guidance; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways