Permethrin: what it treats, how to use it, side effects
Last updated September 3, 2026.
Permethrin is a scabicide and pediculicide - it kills the mites that cause scabies and the lice that live in hair. The prescription cream and the over-the-counter lotion are different products for different jobs, and the technique matters more than the medicine.
What does it treat?
Scabies in adults and children 2 months and older (the prescription cream), and head lice in adults and children 2 months and older (the OTC lotion). Usually one treatment does it; a second is sometimes needed.
How do you take it?
For scabies with the cream: apply a thin layer over all skin from the neck down to the toes - soles included, every skin fold, between fingers and toes, around the waist and buttocks. For babies and adults over 65, add the scalp, hairline, temples, and forehead. You may need the whole tube. Leave it on 8 to 14 hours, then wash it off in a bath or shower. If live mites are still visible 14 days later, repeat once. For lice with the lotion: shampoo first with no conditioner, towel-dry to damp, shake the bottle, keep eyes closed and covered, apply starting behind the ears and back of the neck, cover all hair and scalp, set a 10-minute timer, then rinse in a sink - not the shower, so it stays off the rest of the body - and comb out the dead lice and nits. If live lice appear at 7 days or later, repeat. Both products: skin, hair, and scalp only - never in eyes, nose, ears, mouth, or vagina, never on eyebrows or eyelashes, and flush eyes with water immediately if contact happens. Itching after scabies treatment is normal and does not mean failure.
Side effects to know
- Common: itching, redness, swelling, burning, stinging, or mild rash where it was applied - usually the dying mites or lice, not the medicine.
- Serious - call your doctor: continued irritation of the eyes after flushing, trouble breathing, or any sign of a serious skin reaction like blistering or spreading rash.
Who should not take it?
Anyone allergic to permethrin, pyrethrin, or chrysanthemums - they are chemical cousins. Babies under 2 months are too young. For everyone, eyes and mucous membranes are out. Tell your doctor if you are pregnant or breastfeeding before treating.
When is it an emergency?
Trouble breathing or a spreading blistering rash after application means emergency care. Eye contact that still irritates after a thorough flush is the call-your-doctor version. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
What a Pymander AI doctor consult looks like
Illustrative example, not a real member's messages.
Common questions
Why am I still itchy after the permethrin treatment worked?
Because the itch is your immune system reacting to the mites and what they left behind - and that reaction outlives the mites. MedlinePlus says skin may be itchy after treatment and that this does not mean the treatment failed. The failure signal is specific: live mites or new burrows 14 days or more after treatment. That is what earns a second application, not the itch.
Why do I have to apply the cream from my neck to my toes?
Scabies mites burrow anywhere on the body, and a missed patch is where the infestation survives. MedlinePlus's steps: thin layer over all skin from neck to toes, including soles, between fingers and toes, around the waist and buttocks - and for babies and adults over 65, the scalp, hairline, temples, and forehead too. You may need the entire tube. Then it stays on 8 to 14 hours before washing off.
Why does the lice lotion have so many rules about rinsing?
Because it belongs on the scalp and nowhere else. MedlinePlus's method: rinse in a sink, not a shower or bathtub, so the lotion does not wash over the rest of your body; keep eyes closed and covered through the whole process; and skip conditioner beforehand because it keeps the treatment from working as well. Ten minutes on, then out.
Why didn't one treatment kill all the lice?
Permethrin kills live lice well but eggs can survive and hatch later. That is why the rule is observational: live lice seen 7 days or more after the first treatment means repeat the whole process once. The fine-toothed comb after treatment removes dead lice and nits and is how you know what you are looking at in the days after.
Why did my doctor ask if anyone else in the house is itchy?
Scabies spreads through close contact and shared bedding - treating one person while the mite circulates through the household is how it comes back. Close contacts usually get evaluated at the same time, and the bedding-and-clothing hot wash is part of the treatment, not an optional extra.
What happens if I get permethrin in my eyes?
Flush with water right away - and if the eyes are still irritated after flushing, call your doctor or get medical help. That is the MedlinePlus instruction verbatim. The prevention is application discipline: towel over the face during the lice treatment, eyes closed, and never use it on eyebrows or eyelashes no matter what the internet suggests.