Permethrin — NZ Medication Guide

What is Permethrin?

Permethrin (generic name: permethrin) is a medication used primarily for treatment of scabies and head lice. Permethrin 5% cream (for scabies) is prescription-only in New Zealand. Permethrin 1% (for head lice, e.g. Quellada) is available OTC. Both are funded by Pharmac where applicable.

What is Permethrin Used For?

Permethrin is prescribed by healthcare professionals in New Zealand for the following indications:

• Scabies (Sarcoptes scabiei mite infestation)
• Head lice (Pediculus humanus capitis)
• Body lice (Pediculus humanus corporis)
• Pubic lice (Phthirus pubis)

How Does Permethrin Work?

Permethrin is a synthetic pyrethroid insecticide and acaricide. It disrupts sodium channel function in the nerve cell membranes of insects and mites, causing repetitive nerve firing, paralysis, and death. Permethrin has low mammalian toxicity because human sodium channels are much less sensitive to pyrethroids and the compound is rapidly metabolised by skin enzymes.

How to Take Permethrin

For scabies (5% cream): apply to the whole body from the neck downward, including skin folds, under nails, and between fingers and toes. Leave on for 8–12 hours (overnight) then wash off thoroughly. A second application is required 1 week later. All household members must be treated simultaneously. Launder clothing and bedding on a hot cycle. For head lice (1% cream rinse): apply to damp hair, leave 10 minutes, then rinse. Repeat after 7–10 days. Use a nit comb after application.

Common Side Effects

• Skin itching or stinging (may worsen temporarily after scabies treatment — expected)
• Burning or tingling at application site
• Mild skin numbness
• Skin rash
• Eye irritation if product contacts eyes

Serious Side Effects — Seek Medical Attention

• Allergic contact dermatitis — widespread rash or urticaria
• Anaphylaxis (very rare)
• Seizures if ingested in large quantities (rare with correct topical use)

Drug Interactions

• No significant systemic drug interactions with standard topical use
• Other topical insecticides — avoid concurrent use without medical advice
• Chrysanthemum allergy — permethrin is pyrethroid-based; use with caution in sensitised individuals

New Zealand Prescribing Information

Scabies is a significant public health concern in NZ, particularly in communities with overcrowded housing. BPAC NZ emphasises the importance of treating all household members simultaneously and laundering clothing and bedding to prevent reinfestation. Post-scabetic itch can persist for up to 4 weeks after successful treatment and does not indicate treatment failure. Ivermectin may be considered for outbreaks or treatment-resistant cases by a specialist.

Frequently Asked Questions

Why is my skin still itchy after treating scabies?

Post-scabetic itch is very common and can persist for 2–4 weeks after successful treatment. The immune reaction to dead mite proteins continues after the mites are killed. This does not mean treatment failed. An antihistamine (loratadine or cetirizine) and mild hydrocortisone cream can help. If symptoms worsen significantly or new burrow tracks appear after 4 weeks, see your doctor for reassessment.

Do I need to treat everyone in the household for scabies?

Yes — all household members and close physical contacts should be treated simultaneously, even without symptoms. Scabies has a 4–6 week incubation period and asymptomatic contacts can reinfect treated individuals. Bedding and clothing worn in the previous 3 days should be washed on a hot cycle or bagged for 72 hours.

References & Further Information

The following New Zealand and international resources were used to inform this page:

• New Zealand Formulary — Permethrin
• Pharmac — Funded Medicines Schedule
• BPAC NZ — Scabies Management
• Health New Zealand — Scabies Information

Reviewed by a Registered Pharmacist — KiwiMeds New Zealand