Lice

Topic Overview

What are lice?

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

Three different kinds of lice live on humans:

• Head lice are usually found in hair, most often on the back of the neck and behind the ears. Head lice are common in preschool and elementary school-age children. Adults can get them too, especially adults who live with children.
• Pubic lice , also called crabs, are usually found in the pubic area. But they 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 (nits) in the seams of clothing. The lice are on the body only when they feed.

What causes a lice infestation?

Lice spread easily from one person to another through close contact or through shared clothing or personal items (such as hats or hairbrushes). A louse cannot jump or fly.

What are the symptoms?

The most common symptom of lice is itching. There are different symptoms, depending on which type of lice you have.

• Head lice may not cause any symptoms at first. Itching on the scalp may start weeks or even months after lice have started to spread. Scratching can make the skin raw. The raw skin may ooze clear fluid or crust over, and it may get infected.
• Pubic lice cause severe itching. Their bites may cause small marks that look like bruises on the torso, thighs, or upper arms. If pubic lice get on the eyelashes, the edges of the eyelids may be crusted. You may see lice and their eggs at the base of the eyelashes.
• Body lice cause very bad itching, especially at night. Itchy sores appear in the armpits and on the waist, torso, and other areas where the seams of clothes press against the skin. The lice and eggs may be found in the seams of the person's clothing but are generally not seen on the skin.

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

How is a lice infestation diagnosed?

A doctor can usually tell if you have lice by looking closely for live lice or eggs in your hair. He or she may look at the lice or eggs under a microscope to be sure.

Your doctor can also find pubic lice and body lice by looking closely at your body or your clothing.

How is it treated?

The most common treatment is an over-the-counter or prescription cream, lotion, or shampoo. You put it on the skin or scalp to kill the lice and eggs. In some cases, you may need treatment a second time to make sure that all the eggs are dead. If two or more treatments don't work, your doctor may prescribe a pill called ivermectin.

It's also important to wash clothing and bedding in hot water to help get rid of lice.

Some people have an allergic reaction to lice bites that causes itching for 7 to 10 days after the lice and eggs have been killed. Steroid creams or calamine lotion can relieve the itching. If you have severe itching, you can try antihistamine pills. But don't give antihistamines to your child unless you've checked with the doctor first.

Cause

Lice are very easily spread, usually through close personal contact. Lice infestation may be caused by any of the three types of lice:

• Head lice may be spread through close personal contact, shared personal items (combs, brushes, hats, helmets, clothing, or earphones), or shared bedding.
• Pubic lice are spread mainly through sexual contact and are very contagious. Most people become infected after a single exposure to an infected person. But the lice and eggs may survive long enough on personal items such as clothing or towels to be spread to another person. A child diagnosed with pubic lice may have a history of sexual abuse.
• Body lice are most often spread by contact with personal items, especially clothing and hats. They are occasionally spread by direct personal contact.

Symptoms

Itching, the most common symptom of all types of lice infestation, is caused by an allergic reaction. Lice bite the skin to feed on a person's blood. The saliva from these bites causes the allergic reaction and itching.

Itching may not occur right away, depending on a person's sensitivity and history of lice infestation. The first time a person is infested with lice, it may take several weeks or months for itching to develop or to be noticed. In a repeat case of lice, a person may begin to itch within 2 days of infestation because the immune system reacts more quickly when exposure has occurred previously.

Some people become very sensitive to lice bites and have unbearable itching. Others build up tolerance to the bites and have little or no itching, even with repeated infestations.

In addition to itching, symptoms of lice infestation vary depending on which type of lice is present.

Head lice

Head lice and their eggs (nits) can be seen on hair , the nape of the neck, and behind the ears. They can vary in color from white to brown to dark gray. The eggs are tiny round or oval shapes that are tightly attached to the hair near the scalp and do not slide up and down on the hair.

Frequent scratching may cause broken skin or sores to form on the scalp. The damaged skin may weep clear fluid or crust over, and it may become infected. In response to infection, the lymph nodes behind the ears and in the neck may become tender and swollen.

Pubic lice

A pubic lice infestation may cause itching around the genitals as well as the anus, armpits, eyelashes, and other body areas with hair. Pubic lice bites may cause small, flat, blue-gray, bruiselike marks (maculae cerulea) on the torso, thighs, or upper arms. The marks may last for several months, even after all lice have been killed. Pubic lice, like head lice, can be seen on shafts of hair.

Pubic lice that infest the eyelashes and eyelids may cause irritation and crusting in those areas. The lice may be visible near the base of eyelashes.

Up to one-third of people who have pubic lice also have some other sexually transmitted disease (STD).¹ Symptoms of STDs can include itching, tingling, burning, or pain of the genitals. For more information about STDs, see the topic Exposure to Sexually Transmitted Diseases.

Body lice

Itchy sores from body lice usually develop in the armpits, around the waist, and along the trunk where seams of clothes press against the skin. The lice and eggs are generally not seen on the skin but may be found in the seams of the person's clothing.

Other conditions, such as dandruff or scabies, can cause symptoms similar to those of a lice infestation.

What Happens

Lice will not go away without treatment. If the initial treatment does not kill all of the eggs (nits), a follow-up treatment may be required 7 to 10 days later to kill the newly hatched lice. Itching may last for 7 to 10 days even after successful treatment.

After treatment, dead eggs may remain in the person's hair until they are removed. Some schools have a policy of not allowing children to return to school until they are free of eggs.

If your child has lice, report it to your child's day care provider or school. Other children should be checked, so they can be treated to help prevent new and recurrent infestations.

Complications

Frequent scratching can cause mild complications such as skin infections. In severe cases, hair may fall out. Some people may develop thickened, darkened skin in areas that are infested with lice over a long period.

What Increases Your Risk

Factors that increase the risk of getting lice include:

• Attending school or day care. Young children in school or day care often play together closely and share hats, brushes, and other items. This behavior puts them at a higher risk for getting and transmitting head lice .
• Living in crowded or unclean conditions. People who live in crowded conditions and who do not or cannot bathe and wash their clothing regularly (such as people who are homeless, victims of war or natural disasters, or refugees) are at increased risk for body lice .
• Having many sex partners, which increases the risk for pubic lice .

When To Call a Doctor

If you suspect lice infestation (pediculosis), you can try a nonprescription medicine or visit your doctor to double-check your symptoms. Call a doctor if:

• You have severe nighttime itching that does not go away after a few days.
• You see live lice or new eggs (nits) after using the medicine (prescription or nonprescription).
• You develop serious side effects after using a product to treat lice.
• Signs of a skin infection develop. These may include:
  • Increased pain, swelling, heat, redness, or tenderness.
  • Red streaks extending from the affected area.
  • Continued discharge of pus.
  • Fever of 100 °F (37.8 °C) or higher with no other obvious cause.

Many medicines that treat lice can be harmful if overused or used improperly. Follow the directions exactly as labeled. Never use a product more than twice (with at least 7 days between each use) without first consulting a doctor.

Watchful Waiting

Lice will not go away without proper treatment. Even if they don't bother you much, lice can be spread to other household members, sex partners, or other people you may have close personal contact with. If you think you have lice, try a nonprescription medicine or call a doctor.

Who To See

If you need help treating a lice problem, contact any of the following:

• Local health department
• Nurse practitioner or physician assistant
• Internist
• Pediatrician
• Family medicine doctor
• Gynecologist (for pubic lice)
• Dermatologist

A pharmacist can answer your questions about medicines that treat lice.

To prepare for your appointment, see the topic Making the Most of Your Appointment.

Exams and Tests

Close visual examination for live lice or their eggs (nits) on the hair is usually all that is needed to diagnose a lice infestation (pediculosis). But the doctor may examine the lice or eggs under a microscope to confirm the diagnosis.

Treatment Overview

Lice will not go away without proper treatment. Treatment should begin as soon as symptoms of lice are noticed or when live lice and eggs (nits) are seen on the person's body or in clothing. Specific treatment depends on the type of lice infestation.

• Head lice and pubic lice are destroyed with over-the-counter or prescription medicines applied to the skin or scalp, and sometimes with the prescription pill ivermectin. The most common way to treat lice is to use medicated creams, lotions, or shampoos that kill lice.
• Body lice , which live and lay eggs in the seams of clothing, are destroyed by washing clothing in hot water [130 °F (54.4 °C) or higher] for 5 minutes or more. This will usually kill adult lice and prevent eggs from hatching. Body lice are only present on the skin when they feed and will usually go away on their own if you bathe daily and wear clean clothes. Medicines to kill body lice are usually not needed.

Usually, children with head lice return to school or day care after their first treatment. But some schools have a 'no nits' policy. In this case, the child can only return to school or day care after eggs have been removed. "No nits" policies are discouraged by both the American Academy of Pediatrics and the National Association of School Nurses.² Most doctors agree that a child should be allowed to return to class after proper treatment and should be urged to avoid close head-to-head contact with other students. Confidentiality should be maintained so as not to embarrass a child who has head lice.

Itching may continue even after all lice are destroyed. This happens because of a lingering allergic reaction to their bites. Over-the-counter cortisone (corticosteroid) creams or calamine lotion may help. For severe itching, antihistamine medicines (such as Benadryl) or stronger, prescription-strength corticosteroid creams may be needed. Don't give antihistamines to your child unless you've checked with the doctor first. And don't use cortisone cream for longer than 7 days without talking with your doctor. Do not use the cream on children younger than age 2 unless your doctor tells you to. And don't use it in the rectal or vaginal area in children younger than age 12 unless you've checked with the doctor first.

What To Think About

Who should be treated?

• Household members and anyone who has been in close contact with a lice-infested person should be examined for signs of lice. If they have itching and skin sores that are commonly seen with lice infestations or if lice or eggs are found on their bodies, treatment is recommended.
• Anyone who has shared a bed with a person who has lice should be treated, whether they have symptoms or not.
• If lice recur after treatment, everyone in the household should be treated again with medicine.
• People who have pubic lice are encouraged to tell their sex partners so that they can also be treated. It is also a good idea to see a health professional to be tested for other sexually transmitted diseases. Up to one-third of people who have pubic lice also have some other sexually transmitted disease.¹

Prevention

Head lice can affect people of any income or social level. It is very difficult to prevent lice from spreading among children because they commonly share hats, combs, and other items. Frequently examining the scalps of your school-age children may help you discover and treat lice before they spread to the rest of your family. Avoiding prolonged close contact with a person who has lice will also reduce your risk.

Pubic lice are spread primarily among people who have many sex partners. Reducing the number of sex partners you have may help reduce your risk of getting pubic lice.

Body lice may be prevented by bathing regularly and changing clothes daily. Body lice live on clothing, not on the body. Washing clothing in hot water [130 °F (54.44 °C) or higher] will usually kill adult lice and prevent eggs from hatching. Body lice that are on the skin usually go away on their own with daily bathing and wearing clothes that are not contaminated. Medicines to kill body lice are usually not necessary.

Home Treatment

Home treatment with nonprescription medicines can usually get rid of lice. These medicines include:

• Nix (permethrin 1% creme rinse).
• Rid, Pronto, A-200, R&C, or Triple X (shampoos and gels with pyrethrins and piperonyl butoxide).

If nonprescription methods are not working, a stronger medicine may be needed. Your doctor may prescribe a more concentrated (5% instead of 1% nonprescription) form of permethrin (Elimite), malathion lotion, or a shampoo that contains pyrethrins and piperonyl butoxide.

Doctors in the United States recommend using a lotion or shampoo to kill the eggs and lice. In Britain, where lice have become resistant to medicated lotions and shampoos, one study found that using special fine-toothed combs with a conditioner helped get rid of head lice.³ You may choose to remove the eggs through combing to improve your or your child's appearance. Cleaning combs, brushes, clothing, and other objects can help prevent lice from spreading to other members of your household.

Medications

There are both over-the-counter medicines and prescription products 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. Doctors sometimes prescribe the pill ivermectin to treat lice when two or more approved topical medicines have not been effective.

Permethrin 1% creme rinse (such as Nix) is 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 medicine, keep in mind:

• A second treatment 7 to 10 days after the first treatment is usually recommended to ensure that any newly hatched lice are also killed.
• 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, applying petroleum jelly (such as Vaseline) to the eyelashes several times a day for a week can kill the lice.

In general, drugs are not needed to treat body lice-since the lice live in clothing, not on the body-unless the person is severely infested. The most common way to kill body lice and eggs is to wash clothing and bedding in hot water [130 °F (54.44 °C) or higher] in an automatic washing machine.

Medication Choices

Over-the-counter products for head and pubic lice

• Permethrin creme rinse 1% (Nix) is a common first choice for treating head lice. It kills lice and their eggs 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.

These over-the-counter products are not meant for children younger than age 2.

Prescription products for head and pubic lice

• Permethrin cream 5% (Elimite) is a cream that is applied to the skin or scalp, left on for 8 to 14 hours, and then rinsed off.
• Malathion lotion (Ovide) is applied to hair, left on for 8 to 12 hours, then rinsed off. If lice are still present 7 to 9 days later, a second treatment must be done.
• Lindane (Kwell, G-Well) is a lotion or a shampoo that should only be used when other products fail to get rid of lice or when a person cannot use any of the other products. Lindane contains potentially harmful toxins that can cause negative side effects when it is not used properly.⁴

A pill called ivermectin is sometimes prescribed to treat lice when the person does not respond to two or more topical treatments (treatments applied directly to the affected area).⁵

Antihistamines (both prescription and nonprescription) can treat the itching that often occurs with lice. These medicines may cause drowsiness. Don't give antihistamines to your child unless you've checked with the doctor first.

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

Prescription medicines such as thiabendazole, crotamiton, or trimethoprim sulfamethoxazole (Bactrim, Septra) are sometimes used to treat head and pubic lice.⁶

What To Think About

It is not necessary to remove lice eggs from hair after treatment with topical medicines, but 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 doctor.

There is some concern that lice are becoming resistant to (can no longer be killed by) permethrin or other medicine used to treat lice infestations. It is also possible that lice may persist after treatment because the medicine 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).

Surgery

There is no surgical treatment for lice at this time.

Other Treatment

Head-shaving helps get rid of head lice. After cutting or shaving the hair, put the hair into a garbage bag right away and seal it so that lice cannot spread to other areas in your home. Head-shaving could cause social problems for girls. It is more commonly used for boys who have lice.

No other treatments (such as using Vaseline or mayonnaise) have been proved safe and effective.

Other Places To Get Help

Organizations

Related Information

• Bedbugs
• Scabies
• Scalp Problems

References

Citations

1. Mathieu ME, Wilson BB (2005). Lice (pediculosis). In GL Mandell et al., eds., Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, 6th ed., pp. 3302-3304. Philadelphia: Elsevier Churchill Livingstone.

2. Frankowski BL, et al. (2002). Head lice. Pediatrics, 110(3): 638-642.

3. Hill N, et al. (2005). Single blind, randomized, comparative study of the Bug Buster kit and over-the-counter prediculicide treatments against head lice in the United Kingdom. BMJ, 331(7513): 384-387.

4. U.S. Food and Drug Administration (2003). FDA advisory: Lindane. American Family Physician, 68(4): 764.

5. Drugs for head lice (2005). Medical Letter on Drugs and Therapeutics, 47(1215/1216): 68-70.

6. Grech C, Lebwohl MG (2006). Pediculosis. In MG Lebwohl et al., eds., Treatment of Skin Disease, 2nd ed., pp. 471-473. London: Mosby Elsevier.

Other Works Consulted

• Abel EA (2005). Parasitic infestations. In DC Dale et al., eds., ACP Medicine, section 2, chap. 8. New York: WebMD.

• Abramowicz M (2007). Drugs for parasitic infections. Treatment Guidelines From the Medical Letter, 5(Suppl): e1-e15.

• Burgess I (2007). Head lice, search date October 2006. BMJ Clinical Evidence. Also available online: http://www.clinicalevidence.com.

• Drutz JE (2004). Arthropods. In RD Feigin et al., eds., Textbook of Pediatric Infectious Diseases, 5th ed., vol. 2, pp. 2835-2840. Philadelphia: Saunders.

• Stone SP, et al. (2008). Scabies, other mites, and pediculosis. In K Wolff et al., eds., Fitzpatrick's Dermatology in General Medicine, 7th ed., vol. 2, pp. 2029-2037. New York: McGraw-Hill.

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