Treatment of lice

Lice are tiny insects that live on humans and survive by feeding on blood. When a large number of lice live and reproduce on a person, it is called an infestation.

Three different kinds of lice infest humans:

• Head lice are usually found in hair, most often on the nape of the neck and behind the ears. Head lice infestation (pediculosis) is common in preschool and elementary school-age children. Adults can be affected, especially if they live in a household with children.
• Pubic lice (“crabs”) are usually found in the pubic area but may also be found on facial hair, on eyelashes, on eyebrows, in the armpits, on chest hair, and, rarely, on the scalp.
• Body lice live and lay eggs in the seams of clothing. The lice are only present on the body when they feed. Under certain conditions, such as may occur during natural disasters or war, body lice may transmit life-threatening diseases such as typhus, relapsing fever, and trench fever.

What causes a lice infestation?

Lice are spread easily from one person to another through close bodily contact or through shared clothing or personal items (such as hats or hair brushes). They can not jump or fly.

What are the symptoms of lice infestation?

The most common symptom of lice infestation (pediculosis) is itching in the affected areas. Symptoms vary depending on which type of lice is present.

• Head lice may not cause any symptoms early in the infestation. Itching on the scalp may develop weeks or even months after lice have infested the person. Scratching infested areas can make the skin raw. The raw skin may weep clear fluid or crust over, and it may become infected.
• Pubic lice cause severe itching of affected areas. Their bites may cause small bruise-like marks (maculae cerulea) on the torso, thighs, or upper arms. Pubic lice most often affect the genitals, but they may also appear in the areas around the anus and armpits, in body and facial hair, and on the eyelashes. If pubic lice infest the eyelashes, the edges of the eyelids may be crusted, and lice and their eggs (nits) may be seen at the base of the eyelashes.
• Body lice cause intense itching, especially at night. Itchy sores appear in the armpits and on the waist, trunk, and other areas where seams of clothes press against the skin. The lice and eggs (nits) may be found in the seams of the person’s clothing but are generally not seen on the skin.

How is lice infestation diagnosed?

A close visual examination for live lice or nits in the hair is usually all that is needed to diagnose an infestation of head lice. A health professional may examine the lice or nits under a microscope to confirm the diagnosis.

Pubic lice and body lice can also be diagnosed with a close visual examination of the affected areas or the person’s clothing.

How is it treated?

Lice and their eggs (nits) must be destroyed to get rid of an infestation. The most common treatment is a topical nonprescription or prescription cream, lotion, or shampoo to kill the lice and eggs. Sometimes a second treatment is needed to make sure that all the eggs are destroyed. When two or more topical treatments have failed to get rid of the lice, a prescription pill called ivermectin can be taken.

A new type of hair sealant that kills head lice by suffocating them is currently under medical review.

Some people have a lingering allergic reaction to lice bites that causes itching for 7 to 10 days after the lice and nits have been destroyed. Corticosteroid creams or calamine lotion may be used to relieve the itching. In the case of severe itching, oral antihistamines may be used.

Frequent scratching can cause a skin infection. In the most severe cases of head lice, hair may fall out, and the skin may darken in the areas infested with lice.

Medications

Both nonprescription medications and prescription products are available to treat head and pubic lice . Most products come as a shampoo, creme rinse, or lotion (topical treatment) that is applied to the affected areas, left on for a period of time, and then rinsed off. A prescription pill (ivermectin) is sometimes used to treat lice when two or more approved topical medications have not been effective.

A new type of hair sealant that kills head lice by suffocating them is currently under medical review.

Permethrin 1% creme rinse (such as Nix) is also a common first method of treating lice because it is safe and effective and continues to kill lice and their eggs (nits) even after the cream has been rinsed off. This product is available without a prescription.

When treating lice with medication, keep in mind:

• A second treatment 7 to 10 days after the first treatment is usually recommended to ensure that any lice that have hatched from eggs are also killed. Two treatments are also recommended for pubic lice.
• Itching may persist even after successful treatment. Do not reapply medicated products unless you are advised to do so by a doctor. Excess use of these products may increase the risk of negative side effects such as nausea, headaches, or more serious side effects.

If lice infest the eyelashes, petroleum jelly can be applied to the eyelashes several times a day for a week to kill the lice.

Generally, drugs are not needed to treat body lice-since the lice live in clothing, not on the body-unless the person is severely infested. Body lice are usually treated by washing clothing and bedding in hot water [130° (54.44°) or greater] in an automatic washing machine.

Medication Choices

Nonprescription products for head and pubic lice

• Permethrin creme rinse (Nix) is a common first choice for treating head lice. It kills lice and their eggs (nits) for 2 weeks or more after it has been rinsed off.
• Shampoos containing pyrethrins and piperonyl butoxide (Pronto, Rid, A-200) are left on the hair for 10 minutes and then rinsed out. A second treatment is needed 1 week after the first to kill newly hatched lice.

A new type of hair sealant that kills head lice by suffocating them is currently under medical review.

Prescription products for head and pubic lice

• Permethrin cream (Elimite) is a cream that is applied to the skin or scalp and left on for 8 to 14 hours.
• Malathion lotion (Ovide) is applied to hair and left on for 8 to 12 hours before rinsing off. A second treatment must be done 7 to 9 days later if lice are still present.
• Lindane (Kwell, G-Well) is used as a lotion or a shampoo. It should only be used when other products fail to get rid of lice or when a person cannot use any of the other products. The shampoo may be used to treat head lice, and the lotion may be used to treat pubic lice.
• Carbaryl , which comes in lotion or shampoo form, is used only in Europe. It currently is not available for human use in the United States or Canada.

A prescription pill called ivermectin sometimes can be used to treat lice when the person does not respond to two or more topical treatments (treatments applied directly to the affected area).

Antihistamines, which help control symptoms of allergies, may be prescribed to treat the itching that often occurs with lice. These medications may cause drowsiness.

If there is a serious skin infection, antibiotics may be needed.

Other products that are less commonly used to treat head and pubic lice include benzyl benzoate, thiabendazole, and crotamiton. Trimethoprim sulfamethoxazole (Bactrim, Septra) is an oral antibiotic that sometimes can also be tried to treat severe cases of head lice.

Precipitated sulfur is not as effective as permethrin or lindane, but many doctors still use this product on very small infants, pregnant women, and nursing women because of safety concerns.

What To Think About

It may not be necessary to remove lice eggs (nits) following treatment, although some people may wish to remove them for cosmetic reasons.

Most products used to treat lice may cause side effects if they are not used properly. Never use a product more than two times (with less than 7 days between uses) without first consulting a health professional.

There is some concern that lice are becoming resistant to (can no longer be killed by) permethrin or other medication used to treat lice infestations.It is also possible that lice may persist after treatment because the medication was not used properly or because the person was reinfected by someone else who was still infected with lice.

In cases where multiple treatments have failed to get rid of lice or where resistance is suspected, some doctors are prescribing combinations of treatments, such as permethrin cream along with trimethoprim sulfamethoxazole (Bactrim, Septra).