Lice [en Español]
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 typically 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. The doctor may also comb through your hair with a fine-toothed comb to help detect lice. He or she may look at the lice or eggs under a microscope.
Your doctor can also find pubic lice and body lice by looking closely at your body or your clothing.
How is it treated?
Lice won't go away on their own. Be sure to do all you can to treat lice and to prevent the spread of lice.
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 different medicine.
It's also important to wash clothing and bedding in hot water to help get rid of lice.
Some people continue to have 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.
Frequently Asked Questions
Learning about lice:
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. The lice and eggs may also survive long enough on personal items such as clothing or towels to be spread to another person. A child who has 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 sometimes spread by direct personal contact.
Lice are spread from human to human. Pets don't get head lice and can't spread them to humans.
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 start 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 before.
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 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.
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 marks (maculae cerulea) that look like bruises 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.
Pubic lice tends to be spread by sexual contact. If you or your teen has pubic lice, you may also have some other sexually transmitted infection (STI). Symptoms of STIs can include itching, tingling, burning, or pain of the genitals. For more information about STIs, see the topic Sexually Transmitted Infections .
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.
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 so that other children can be checked.
Some children and parents think about or feel lice crawling even after the lice problem is gone. If you or your child feels like symptoms are lasting or feels troubled after the lice problem is gone, talk to your doctor.
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
Things 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 an over-the-counter lice 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 have serious side effects after using a product to treat lice.
- You have signs of a skin infection. These may include:
- Increased pain, swelling, heat, redness, or tenderness.
- Red streaks extending from the affected area.
- Discharge of pus.
- Fever of 100°F (37.8°C) or higher with no other obvious cause.
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 have close personal contact with. If you think you have lice, try an over-the-counter lice 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
- Family medicine doctor
- Gynecologist (for pubic lice)
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
To find out if your child has lice, the doctor will do a close visual exam to look for live lice or their eggs (nits) on the hair . The doctor may also use a fine-toothed comb to help detect lice. He or she may need to look at the lice or eggs under a microscope to confirm the diagnosis.
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 killed with over-the-counter or prescription medicines applied to the skin or scalp, and sometimes with a prescription pill. 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 if you bathe daily and wear clean clothes.
Children with head lice can return to school or day care after their first treatment. Some schools have a "no nits" policy in which the child can go back to school or day care only after eggs have been removed. "No nits" policies are discouraged by medical experts. 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 checked 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 you still see live lice on a household member 7 to 10 days after he or she had the first treatment, it's best for that person to have a second treatment. Sometimes the first treatment doesn't work.
- 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 doctor to be tested for other sexually transmitted infections .
Treatment is not likely to work if:
- You don't use the medicine as directed.
- You stay in contact with other people who have lice but who did not get treated.
- Lice become resistant to the medicines and don't die. This occurs in some locations more than others. Talk to your doctor if you think a lice medicine isn't working as expected.
Head lice are easily spread among children because kids commonly share hats, combs, and other items. If you or your child has head lice, you can help prevent others from getting it if you avoid head-to-head (hair-to-hair) contact during activities inside the home and outside the home. Also, don't share clothing, bedding, hair brushes and accessories, pillows, stuffed animals, or towels. 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 needed.
To help control the spread of lice, you can also clean combs, brushes, clothing, and other personal items to kill lice and their eggs.
There are both over-the-counter medicines and prescription products to treat head lice 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 a pill to treat lice when two or more approved topical medicines have not worked.
If lice infest the eyelashes, your doctor may prescribe an eye ointment for you.
Because body lice live in clothing, not on the body, medicines are generally not needed 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 (54.5°C) or higher] in a washing machine.
Over-the-counter (OTC) medicines that are recommended for head or pubic lice include: footnote 1
- Permethrin creme rinse 1% (such as Nix), which 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 (such as Rid), which are left on the hair for 10 minutes and then rinsed out. A second treatment is needed 9 days after the first to kill newly hatched lice.
There are other OTC products for lice , but not all of them have good evidence that their benefits outweigh the side effects and other risks. Check the product label . Be sure to follow the directions about proper use and safety. And talk to your doctor or pharmacist about whether these products are safe for young children.
Prescription medicines that are recommended for head or pubic lice include: footnote 1
- Benzyl alcohol 5% (Ulesfia), which is used to treat head lice. It is applied to the hair on the head, left on for 10 minutes, and then rinsed off.
- Malathion lotion (Ovide), which is used to treat head lice. It is applied to hair on the head, 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.
If these OTC or prescription medicines aren't working, your doctor may prescribe a different medicine to help get rid of lice. These include ivermectin (Sklice or Stromectol), permethrin 5% (Elimite), and spinosad (Natroba). In rare cases, lindane may be prescribed. But lindane is falling out of favor because of the potential for serious nervous system side effects. The American Academy of Pediatrics no longer recommends lindane as a treatment for head lice.
Antihistamines (both prescription and nonprescription) can help relieve 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.
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.
Wet combing is an option for infants who can't use lice medicines.
Some people try other treatments (such as using petroleum jelly or olive oil to smother lice). But there is not strong evidence that other treatments such as these work well or are safe to treat lice.
Head-shaving helps get rid of head lice. But this method can cause distress to the person whose head is shaved. 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.
Other Places To Get Help
- Drugs for parasitic infections (2010). Treatment Guidelines From The Medical Letter, 8(Suppl): e1–e20.
Other Works Consulted
- American Academy of Pediatrics (2015). Pediculosis capitis. In DW Kimberlin et al., eds., Red Book: 2015 Report of the Committee on Infectious Diseases, 30th ed., pp. 597–601. Elk Grove Village, IL: America Academy of Pediatrics.
- Burgess I (2011). Head lice, search date June 2010. Online version of BMJ Clinical Evidence. Also available online: http://www.clinicalevidence.com.
- Diaz JH (2010). Lice (pediculosis). In GL Mandell et al., eds., Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, 7th ed., vol. 2, pp. 3629–3632. Philadelphia: Churchill Livingstone Elsevier.
- Drutz JE (2009). Arthropods. In RD Feigin et al., eds., Feigin and Cherry's Textbook of Pediatric Infectious Diseases, 6th ed., vol. 2, pp. 3033–3039. Philadelphia: Saunders Elsevier.
- Elston D (2011). Infestations. In EG Nabel, ed., ACP Medicine, section 4, chap. 8. Hamilton, ON: BC Decker.
- Frankowski BL, et al. (2010). Clinical report: Head lice. Pediatrics, 126(2): 392–403.
- Gupta A, Levitt JO (2010). Pediculosis. In MG Lebwohl et al., eds., Treatment of Skin Disease: Comprehensive Therapeutic Strategies, 3rd ed., pp. 536–539. Edinburgh: Saunders Elsevier.
- Habif TP (2010). Infestations and bites. In Clinical Dermatology: A Color Guide to Diagnosis and Therapy, 5th ed., pp. 581–634. Edinburgh: Mosby Elsevier.
- Habif TP, et al. (2011). Infestations and bites. In Skin Disease: Diagnosis and Treatment, 3rd ed., pp. 334–365. Edinburgh: Saunders.
- Morelli JG (2011). Arthropod bites and infestations. In RM Kleigman et al., eds., Nelson Textbook of Pediatrics, 19th ed., pp. 2317–2322. Philadelphia: Saunders.
- Spinosad (Natroba) topical suspension for head lice (2011). Medical Letter on Drugs and Therapeutics, 53(1367): 50–51.
- 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.
Primary Medical Reviewer John Pope, MD - Pediatrics
Specialist Medical Reviewer Susan C. Kim, MD - Pediatrics
Current as ofNovember 20, 2015
Current as of: November 20, 2015
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