What is "permethrin"

n. A synthetic insecticide, C₂₁H₂₀Cl₂O₃, used to treat head louse, nits, scabies, and in flea collars.

Permethrin is a medication and chemical widely used as an insecticide, acaricide, and insect repellent. Permethrin is a first-line treatment for scabies. It is used as a cream.

It belongs to the family of synthetic chemicals called pyrethroids and functions as a neurotoxin, affecting neuron membranes by prolonging sodium channel activation. It is not known to rapidly harm most mammals or birds, but is toxic to fish and cats. In cats it may induce hyperexcitability, tremors, seizures, and death. In general, it has a low mammalian toxicity and is poorly absorbed by skin.

It is on the World Health Organization's List of Essential Medicines, the most important medications needed in a basic health system.