Pediculosis (Lice Infestation)

The three types of lice

Nits are eggs glued to hair shafts close to the scalp. They are oval and white to yellow-brown, and unlike dandruff, they do not brush off easily.

Head lice

Head lice are most common in children aged 3 to 11 and their families. They crawl, not jump or fly, and spread mainly by direct head-to-head contact. They have nothing to do with cleanliness.

Symptoms:

• itching of the scalp, which may take 4 to 6 weeks to start after a first infestation
• a tickling or crawling feeling
• sores from scratching, sometimes infected
• trouble sleeping, as lice are more active in the dark

Body lice

Body lice live and lay eggs in clothing seams, visiting the skin only to feed. They are linked to crowded living conditions and lack of access to bathing and clean clothing.

Symptoms:

• intense itching
• red bites, especially around the waist, shoulders and armpits
• thickened, darkened skin in long-standing cases

Body lice can spread diseases, including epidemic typhus, trench fever and louse-borne relapsing fever.

Pubic lice

Pubic lice are usually spread through sexual contact. They can also be found in other coarse body hair, including eyelashes and eyebrows.

Symptoms:

• itching in the genital area, often worse at night
• small blue-gray spots on the skin from bites
• visible lice or nits in pubic hair

Anyone with pubic lice should be tested for other sexually transmitted infections.

Diagnosis

Lice are diagnosed by finding a live louse. Wet-combing the hair with conditioner and a fine-toothed lice comb is the most reliable method. Nits within about 6 mm (1/4 inch) of the scalp suggest active infestation. Nits further out are usually empty or dead. A doctor can confirm with a magnifying glass. Conditions that can look similar include dandruff, hair casts, scabies and impetigo.

Treatment

Head lice

Follow product directions exactly. Options include:

• permethrin 1% lotion or pyrethrins with piperonyl butoxide: over the counter. Some lice are now resistant.
• ivermectin 0.5% lotion: a single application, available without prescription in the US.
• spinosad and malathion: prescription options, effective against resistant lice.
• oral ivermectin: occasionally used for difficult cases.

Many treatments need a second application 7 to 9 days later to kill newly hatched lice. Do not use extra products or combine treatments unless advised.

Wet combing: combing conditioner-coated hair with a fine-toothed lice comb every 3 to 4 days for 2 weeks can remove lice without chemicals, and helps alongside treatment.

Around the home:

• wash bedding, hats and clothing used in the past 2 days in hot water, at least 54 °C (130 °F), and dry on high heat
• seal items that cannot be washed in a plastic bag for 2 weeks
• soak combs and brushes in hot water for 10 minutes
• vacuum floors and furniture. Fumigant sprays are not needed

Children can usually return to school after the first treatment. No-nit policies are not recommended by the American Academy of Pediatrics.

Body lice

• bathe and change into clean clothes
• wash clothing and bedding in hot water and dry on high heat, or seal for 2 weeks
• lice-killing medicines are usually not needed once clothing is treated

Pubic lice

• permethrin 1% or pyrethrins, applied to all affected areas and rinsed off after 10 minutes, repeated in 9 to 10 days
• ivermectin by mouth as an alternative
• for eyelashes: petroleum jelly applied to the lid margins twice daily for 10 days, as advised by a doctor
• treat sexual partners at the same time and avoid sex until treatment is complete
• wash bedding and clothing

Itching

Itching can last a week or more after successful treatment. An oral antihistamine or mild steroid cream may help.

Frequently asked questions

How do I know if I have lice or nits?

Look for live lice moving on the scalp or body hair, or oval eggs glued firmly to hair shafts close to the skin. Wet-combing with conditioner and a fine lice comb is the best way to find them. Dandruff flakes brush off easily, while nits do not.

How do lice spread?

Head lice spread mainly through direct head-to-head contact, less often through shared hats, combs or bedding. Body lice spread through shared clothing and bedding. Pubic lice spread mostly through sexual contact. Pets do not spread human lice.

What is the best treatment for head lice?

Over-the-counter permethrin, pyrethrins or ivermectin lotion work for most people when used as directed. Prescription options like spinosad and malathion are effective against resistant lice. Combining treatment with careful wet-combing improves success.

Do I need to clean my whole house for lice?

No. Lice cannot survive long off the body. Wash bedding, clothing and hats used in the past 2 days in hot water, soak combs, seal unwashable items for 2 weeks and vacuum. Pesticide sprays are unnecessary.