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# 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.

Updated Nov 1, 2026

## 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)

## Key points

- Treat every household member and close contact at the same time, even without symptoms, and wash bedding and clothing hot (or seal them in a bag).
- Itch can last for weeks after a successful treatment (reaction to dead mites); it is not by itself a reason to re-treat.
- Crusted (Norwegian) scabies in immunosuppressed people is highly contagious and needs topical plus oral treatment.
- Lice resistance to permethrin is widespread; wet combing or other agents are used when it fails.
- Lindane can cause seizures; it is second line only and is avoided in premature infants and people with seizure disorders.

## Drugs in this class

- [**Permethrin** A 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](https://durgical.com/en/pharmacology/permethrin/)
- [**Benzyl benzoate** A 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)](https://durgical.com/en/pharmacology/benzyl-benzoate/)
- [**Lindane** An 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)](https://durgical.com/en/pharmacology/lindane/)
- [**Malathion** An organophosphate lotion that kills head lice and their eggs by blocking their acetylcholinesterase. It is flammable… Acetylcholinesterase of the louse](https://durgical.com/en/pharmacology/malathion/)

## 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.

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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](https://www.who.int/news-room/fact-sheets/detail/scabies) (World Health Organization, 2026); [Scabies: Diagnosis and Treatment with Images](https://dermnetnz.org/topics/scabies) (DermNet, 2026); [Head lice and nits](https://www.nhs.uk/conditions/head-lice-and-nits/) (NHS, 2026).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/classes/scabicides-and-pediculicides/