Scabicides and pediculicides
Topical insecticides that kill the scabies mite or lice by poisoning their nervous system. The whole household is treated at the same time.
What they are
Medicines applied to the skin or hair to kill Sarcoptes scabiei (scabies) and lice (head, body and pubic). Permethrin cream is first line for scabies; benzyl benzoate lotion is the WHO-listed alternative; lindane (second line because of neurotoxicity) and malathion (head lice) are older agents. Oral ivermectin (its own page) is used for crusted scabies, outbreaks and mass treatment.
Mechanism of action
Most agents poison the nervous system of the parasite: pyrethroids such as permethrin keep its nerve sodium channels open, malathion blocks its acetylcholinesterase and lindane overstimulates its nerves. Benzyl benzoate is directly toxic to mites and lice. The parasite is paralysed and dies. Treatments do not kill every egg, so a repeat application is often part of the plan.
Target: Nervous system of the mite or louse (voltage-gated sodium channels, acetylcholinesterase)
Drugs in this class
- PermethrinA synthetic pyrethroid cream that paralyses the scabies mite. First-line topical treatment for scabies; also used for…Voltage-gated sodium channel in the nerve membrane of the mite or louse
- Benzyl benzoateA topical lotion that kills the scabies mite. It is the WHO-listed alternative to permethrin; it can burn on…Scabies mite and lice (molecular target not established)
- LindaneAn old organochlorine scabicide and pediculicide that can cause seizures and death. Second line only, used once; no…Nervous system of the mite or louse (neuronal overstimulation)
- MalathionAn organophosphate lotion that kills head lice and their eggs by blocking their acetylcholinesterase. It is flammable…Acetylcholinesterase of the louse
Others in the class
- ivermectin (oral)
- crotamiton
- precipitated sulfur
- spinosad
- dimeticone
Test yourself
Think of the answer, then tap the question to see it.
Why is the whole household treated for scabies at the same time?
Contacts may be infested without symptoms for weeks and would re-infect the index case.
A patient still itches two weeks after correct permethrin treatment, with no new burrows. What is the likely explanation?
A hypersensitivity reaction to dead mites, which can persist for weeks; itch alone is not treatment failure.
Which form of scabies is most contagious, and in whom does it occur?
Crusted (Norwegian) scabies, with very many mites, in immunosuppressed people such as those living with HIV.
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Scabies (World Health Organization, 2026); Scabies: Diagnosis and Treatment with Images (DermNet, 2026); Head lice and nits (NHS, 2026).
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Representative model, for educational purposes only.