Head Lice Information

The American Academy of Pediatrics Guidelines for Management of Head Lice: An In-Depth Guide

Michael R. Page, PharmD, RPh

Learn about the current guideline-recommended treatment options for head lice, including lesser-known guideline-recommended non-drug treatment options.

Head lice is a common condition that is most common in children aged 3 to 12 years. The American Academy of Pediatrics (AAP) has released guidelines for the treatment of head lice.

Lice are wingless, blood-sucking insects with 6 legs. Although lice are commonly thought of as a single entity, many species of lice exist, and each species is highly adapted to a specific type of host. For this reason, transmission of lice from animals to humans is rare.

Mature head lice are fairly large—about 2 to 3 mm in length, or about the size of a sesame seed. Although an adult louse may lay as many 120 eggs, a typical infestation of head lice involves fewer than 20 adult insects.2 For this reason, the eggs of a louse, which may be the same color as hair or appear as white specks on very dark hair, are often easier to locate than the insect. The easiest place to locate eggs is at the border of the hairline on the neck.

Head lice feed on blood extracted from the scalp. In the process of feeding, lice inject a small amount of saliva into the scalp. Sensitization to this saliva typically occurs within 4 to 6 weeks, and the affected person may begin to experience intense scalp irritation and may scratch the scalp frequently.

The entire reproductive cycle of the louse repeats approximately every 3 weeks. Importantly, when away from the scalp, head lice usually survive less than 24 hours,1and cannot reproduce. Hair length, brushing habits, and shampooing habits do not affect the incidence of infestation.

School Attendance

The AAP does not recommend keeping children with head lice home from school, as rates of transmission are very low. Typically, once a case of head lice is detected, children have had lice for at least 1 month, and the AAP recommends that children should remain in class. Simple avoidance of head-to-head contact with other children is a sufficient preventive measure.

Home Cleaning Measures

Advise parents that transmission of head lice through modes other than head-to-head contact is very uncommon. Running bedding through a dryer after washing to achieve temperatures >130°F will kill any lice or nits on bedding. Instruct parents to vacuum, but not to wash, other fabric items, such as couches, carpets, and car seats. Intensive housecleaning is not beneficial.


The AAP recommends choosing a treatment for head lice that is easy to use, safe, and effective, and that kills lice and their eggs quickly. The optimal treatment should also be affordable.

OTC permethrin 1% is the recommended first-line treatment for head lice treatment. Permethrins, unlike pyrethrins, may be used in cases of chrysanthemum allergy.

Pyrethrins (with or without piperonyl butoxide), however, should not be used in cases of true chrysanthemum allergy. Although some products may indicate some cross-sensitivity to pyrethrins in patients with ragweed allergy, the risk of allergic reaction in ragweed-allergic populations is very low, and the AAP authors did not consider ragweed allergy a true contraindication for use.

Instruct patients to leave the product in for at least 10 minutes before rinsing. Most cases of apparent resistance are due to improper use of OTC formulations. However, in cases of true resistance, malathion 0.5% (Ovide) is the next-line guideline-recommended option. Treatment with malathion involves applying the lotion to dry hair and leaving it on the hair for 8 to 12 hours. Typically, the first application of malathion kills lice and also kills many lice eggs. A second application is recommended if lice are observed 7 to 9 days after the first treatment.

It is important to recognize some of the problems associated with the organophosphate malathion 0.5%. Because the formulation of malathion contains a high percentage of isopropyl alcohol, the product is extremely flammable. In fact, flammability issues have led to 2 temporary withdrawals of the product from the US market. As a result, use of any product that heats the hair after application—including hair dryers or curling irons—is contraindicated. Even cigarette smoking near children has ignited hair in some case reports. Ingestion of malathion may lead to neurologic adverse events, so the product should be kept out of the reach of children.

Benzyl alcohol 5% (Ulesfia) is an alternative to malathion that was introduced in 2009. In addition to being indicated for use in younger children (as young as 6 months), the active ingredient in Ulesfia is potentially less toxic than malathion, but unlike malathion, Ulesfia does not kill louse eggs. Instruct patients to apply Ulesfia to the scalp for 10 minutes and to repeat the procedure in 1 week. Some experts recommend a third treatment 1 week later. With appropriate use, Ulesfia cures approximately three-fourths of cases of lice within 14 days.

Lindane 1% has been banned in California, and is no longer recommended by the AAP as a treatment for head lice. If ingested, lindane can lower the seizure threshold. Its use is contraindicated in neonates.1
Crotamiton 10% lotion (Eurax) may cure head lice if applied to the scalp and left on for a full 24 hours, although its use as a pediculicide has not been evaluated by the FDA. Ivermectin (both oral and topical formulations) and sulfamethoxazole-trimethoprim (oral) may be effective against head lice, but are not FDA approved for this indication.

For parents who are concerned about using OTC permethrins or pyrethrins or about the cost, consider recommending a petrolatum shampoo. The petrolatum shampoo procedure involves applying and massaging about 1 ounce of petroleum jelly (roughly the volume of a shot glass) into the hair and scalp. The jelly should then be left on the hair overnight. Caution parents that the petrolatum will not come out of the hair easily, although 7 to 10 days of daily shampooing will generally remove the petrolatum jelly residue. Petroleum jelly is not an FDA-approved treatment, but it is highly effective against head lice and is an acceptable AAP-recommended treatment.

For a potentially less messy cure for head lice, 1 study showed that application of Cetaphil Gentle Skin Cleanser to the hair followed by blow-drying to dry the cleanser, leaving the dried product on the hair overnight, and repeating the procedure once weekly for 3 weeks led to a 96% rate of treatment success.

Another nondrug option is the AirAllé device. This FDA-cleared treatment is generally administered at selected treatment centers across the United States.

No known lice treatment kills all lice eggs. Therefore, combing an affected child’s hair with a fine-toothed nit comb may be a beneficial adjunct to treatment. Although the comb will not remove all eggs, it will mechanically damage the eggs, preventing hatching. Applying vinegar to the hair before combing may help loosen the eggs from the hair shaft.

Electric combs are marketed, but studies to verify the efficacy of these combs have not been conducted.

In Summary

For the treatment of lice, recommend an OTC permethrin- or pyrethrin-based product. Remember to instruct parents to leave the treatment in the hair for at least 10 minutes. Keep in mind that no treatment—prescription or nonprescription—is proven to kill all lice eggs. Instruct parents to use a fine-toothed nit comb to mechanically damage lice eggs and prevent them from hatching.

For parents who are concerned about using a chemical product, consider recommending 3 weekly applications of Cetaphil Gentle Skin Cleanser. The lotion should be dried with a hair dryer after application, and left on overnight.

In addition to advising parents on treatment, and explaining the safe use of treatments, pharmacists can clarifying appropriate home cleaning measures and school attendance policies, as recommended by the AAP.

Mayo Clinic – Head Lice Information


Head lice are tiny insects that feed on blood from the human scalp. An infestation of head lice, called pediculosis capitis, most often affects children and usually results from the direct transfer of lice from the hair of one person to the hair of another.

A head lice infestation isn’t a sign of poor personal hygiene or an unclean living environment. Head lice don’t carry bacterial or viral infectious diseases.

Over-the-counter and prescription medications are available to treat head lice. Following treatment instructions carefully is important for ridding your scalp and hair of lice and their eggs.

A number of home or natural remedies are used to treat head lice infestations, but there is little to no clinical evidence of their effectiveness.


You may not be aware of a lice infestation. However, common signs and symptoms can include:

  • Itching Itching on the scalp, neck and ears is the most common symptom. This is an allergic reaction to louse saliva. When a person has an infestation for the first time, itching may not occur for two to six weeks after infestation.
  • Lice on scalp Lice may be visible but are difficult to spot because they’re small, avoid light and move quickly.
  • Lice eggs (nits) on hair shafts Nits stick to hair shafts. Incubating nits may be difficult to see because they’re very tiny. They’re easiest to spot around the ears and the hairline of the neck. Empty nits may be easier to spot because they’re lighter in color and further from the scalp. However, the presence of nits doesn’t necessarily indicate an active infestation.

When to see a doctor

See your doctor before you begin treatment if you suspect that you or your child has a head lice infestation. Studies show that many children have been treated for head lice with over-the-counter medications or home remedies when they don’t have an active head lice infestation.

Things often mistaken for nits include:

  • Dead or empty nits from a previous head lice infestation
  • Dandruff
  • Residue from hair products
  • Bead of dead hair tissue on a hair shaft (hair cast)
  • Scab tissue, dirt or other debris
  • Other small insects found in the hair


A head louse is a tan or grayish insect about the size of a strawberry seed. It feeds on human blood that it extracts from the scalp. The female louse produces a sticky substance that adheres each egg to a hair shaft. An egg is attached approximately 3/16 inch (4 millimeters) from the base of the shaft — an environment that provides an ideal temperature for incubating the egg.

The louse life cycle

A louse egg hatches after eight or nine days. What emerges is an immature form of the louse called a nymph. The nymph becomes a mature adult louse after nine to 12 days, and an adult lives for three to four weeks.


Head lice crawl, but they cannot jump or fly. Most often transmission of a head louse from one person to another is by direct contact. Therefore, transmission is most often within a family or among children who have close contact at school or play.

Indirect transmission is not likely, but lice may spread from one person to another by items such as:

  • Hats and scarves
  • Brushes and combs
  • Hair accessories
  • Headphones
  • Pillows
  • Upholstery
  • Towels

Indirect transfer could also occur among items of clothing stored together. For example, hats or scarves hung on the same hook or stored in the same school locker could serve as vehicles for transmitting lice.

Household pets, such as dogs and cats, don’t play a role in spreading head lice.

Risk factors

Because head lice are spread primarily by head-to-head contact, the risk of transmission is greatest among younger people who play or go to school together. In the United States, cases of head lice most often occur in children in preschool through middle school.


If your child scratches an itchy scalp from a head lice infestation, it is possible for the skin to break and develop an infection.


It’s difficult to prevent the spread of head lice among children in child care facilities and schools because there is so much close contact. And the chance of indirect transmission from personal items is slight.

However, it is generally a good practice for children to hang their garments on a separate hook from other children’s garments and not to share combs, brushes, hats and scarves. A worry about head lice transmission is not considered a good reason to avoid sharing protective headgear for sports and bicycling when sharing is necessary.