Malathion

How it works

It is acetylcholinesterase inhibitor that is toxic to lice and mites, and aqueous formulations also have ovicidal activity against louse eggs.

Prescribing in practice

• Aqueous (water-based) formulations are preferred for the face, scalp, broken skin and in asthma, as alcoholic lotions can irritate and may trigger wheezing.
• Apply to the affected area, leave for the recommended contact time and then wash off; a second application is usually advised to kill newly hatched lice.
• For scabies the whole body is treated, and close contacts should be treated simultaneously to prevent reinfestation.

Monitoring

Check for treatment success by detection combing for head lice or symptom resolution for scabies, and assess the skin for irritation.

Counselling the patient

• Follow the recommended contact time before washing the product off.
• Apply a second treatment after about a week to catch newly hatched lice.
• Treat all affected household contacts at the same time.

Evidence & guidelines

Malathion is an established recommended treatment for head lice and scabies, used as an alternative to permethrin where resistance or intolerance occurs.