Permethrin Features

Permethrin, a chemical that kills parasites and eggs, is the active ingredient in medications that treat lice and scabies. Permethrin is very effective in killing parasites, but an additional treatment may be needed one week after the first to ensure that all the parasites are dead. Because the medication contains a strong chemical, it is important to follow your doctor's instructions when using permethrin.

Identification

• Although a parasitic infestation is responsible for both scabies and lice, the two conditions aren't quite the same. Adult lice and eggs are visible to the human eye, while the mites that cause scabies are microscopic. If you have lice, your scalp may itch. You may also notice live adult lice crawling in your hair and may see lice eggs, or nits, stuck to strands of your hair. Although you won't see scabies, you'll know they are there because of intense itching in the skin and a red rash caused when the mites burrow into your skin. Simply washing the skin and hair is not enough to rid your body of these parasites. Doctors prescribe medications containing permethrin, a pesticide first used to treat cotton, to kill the parasites.

Application

• Permethrin is available in lotion and cream form and is intended for external use only. Doctors usually prescribe the liquid to treat lice and the cream to treat scabies. After taking a shower or bath, towel dry your skin and smooth a thin layer of the cream all over your body, starting from your neck and working your way to your feet and toes. Allow the cream to remain on the skin for eight to 14 hours before washing it off. Kids Health from Nemours suggests using a toothbrush to apply the cream under nails.

  The lotion form of permethrin works best on freshly shampooed hair. After towel drying, work the lotion into the scalp, back of the neck and ears. Wait 10 minutes before rinsing. Wearing rubber gloves when applying either form of permethrin can help protect your hands should you have any open cuts.

Side Effects

• Applying permethrin lotion or cream may cause mild redness, itching, stinging, burning, rash, irritation or swelling on your skin. If these symptoms are severe, let your doctor know. Some people may develop an allergic reaction to permethrin and must seek immediate medical attention. Signs of an allergic reaction include trouble breathing, hives, or throat, tongue, lip or facial swelling.

Considerations

• Doctors recommend following up an application of permethrin lotion by carefully combing through the hair with a nit comb to remove adult lice and nits stuck to hair strands. Vacuuming floors and washing bedding, clothing and towels in hot water will help remove any lingering lice. Avoid using the medication if you are allergic to permethrin or to chrysanthemums. Although permethrin is not expected to harm unborn babies, it may harm a nursing baby, Drugs.com reports. Tell your doctor if you are pregnant, nursing or intend to use permethrin on a child younger than 2-months-old before using the medication.