Permethrin is a synthetic pyrethroid and neurotoxin. Permethrin affects the neuronal membrane by blocking the movement of sodium ions from outside to inside the neuronal cell membrane thereby disrupting the sodium channel current that regulates the polarization of the membrane. This leads to delayed repolarization and subsequent paralysis of the nervous system. Permethrin is used to eradicate parasites such as head lice, ticks and scabies from humans and animals.