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Evidence-Based Strategies for Common Clinical Questions

May, 2018

Head Lice Treatment: No Longer a Head-Scratcher

Primary Author: David Skoglund| Chief Pediatric Resident

Column Editor: Rupal Gupta, MD | Medical Director, Operation Breakthrough Clinic | General Academic Pediatrics | Assistant Professor, UMKC 

The head louse is a well-known insect that causes scalp and hair infestations. Approximately 6 to 12 million children are diagnosed each year; most of these children are between 3 and 12 years of age. Diagnosis is made by inspection of the scalp and hair, with identification of the adult louse, which is the size of a sesame seed. Eggs or nits (empty egg casings) are smaller, often compared to the size of a knot in a thread, and are attached firmly to the hair shaft. A louse comb may help facilitate finding both lice and their eggs.

Head lice do not transmit disease and the diagnosis is not associated with poor hygiene, but a child may be stigmatized when a school identifies the child and sends him or her home in an effort to prevent transmission.1Because head lice cause intense pruritus, bacterial superinfection of excoriated scalp may occur. Overall treatment costs in the United States may be as high as $1 billion in direct and indirect losses.2, 3 

While many treatment options exist, topical permethrin and pyrethrin-based products, available over the counter since 1990, have been the mainstay for treatment. Pyrethrin-based products are derived from chrysanthemum extracts and generally formulated with piperonyl butoxide, a common ingredient in insecticides that enhances the effects of pyrethrin. Permethrin 1 percent acts by modifying voltage-gated sodium channels, causing an immobilization effect (knockdown) and eventual death of the louse. Lice with genetic protection to permethrin are insensitive to this effect, but this adaptation is not conclusively linked to treatment failure; 33 to 100 percent of lice in California, Florida and Texas have this gene, as well as 97 percent in Canada.3 

Increasing resistance patterns have resulted in providers seeking alternatives when conventional treatment fails. Topical ivermectin (Sklice) is effective and recommended as a 10-minute application, but is expensive.3 Spinosad 0.9 percent topical suspension (Nataroba), approved in 2011, kills live lice and unhatched eggs. This topical preparation does not require reapplication, but is also as much as 10 times as costly as the over-the-counter preparations and is not approved for children under 4 years of age.1 Malathion lotion, an acetylcholinesterase inhibitor, is effective against lice and their eggs, but resistance is developing in some countries and the medication is not approved for younger children. Antibiotic regimens such as trimethoprim/sulfamethoxazole are not recommended.

Occlusive products such as petroleum jelly, mayonnaise or olive oil have not been well studied. Benzyl alcohol 5 percent lotion (Ulesfia) is a topical pediculicide that was approved in 2009 and is effective, but costly. A non-randomized trial has reported success using Cetaphil™ which, while not approved for use as a pediculicide, was shown to asphyxiate lice after being applied, dried on with a handheld dryer, and washed out the next morning. Increasingly common are lice shops that feature an FDA-cleared machine that uses hot air desiccation, with reported success, but costs may be substantial. Topical dimethicone 4 percent lotion, also an over-the-counter occlusive agent, is a silicone-based organic polymer – one treatment was more efficacious than two treatments with 1 percent permethrin.4 

Recommendations from the American Academy of Pediatrics emphasize that children with head lice not be excluded from school and that pediatricians should take the lead in educating families and schools. Over-the-counter 1 percent permethrin or pyrethrins remain first-line treatments. Repeat treatment is recommended at day nine. If parents refuse a pediculicide, consider occlusive products such as petroleum jelly or Cetaphil, and ensure that parents use proper technique, repeating treatment weekly for at least three weeks with frequent follow-up.6 Benzyl alcohol should not be used for infants younger than 6 months. Treatment of bedmates and identification and treatment of other household members is recommended. In areas with high resistance rates, spinosad or topical ivermectin is recommended.5

Prevention of recurrence is an important step in treatment. While indirect transmission is rare, it is certainly possible. Sheets and clothing should be washed in temperatures of at least 50°C (122°F) to kill all lice and nits.3


Head lice can be a challenging condition to treat for a number of reasons, but effective management can substantially benefit the patient psychologically, as well as physically. Permethrin remains a useful treatment option in areas with low resistance patterns, but topical ivermectin or spinosad should be considered in areas of high resistance.


  1. Management and Treatment of Human Lice. Sangaré AK, Doumbo OK, and Raoult D. BioMed Research International, Vol. 2016, Article ID 8962685, 12 pages.

  2. Human Lice: Their Prevalence, Control and Resistance to Insecticides—A Review, 1985–1997. Gratz NG. Geneva, Switzerland: World Health Organization, Division of Control of Tropical Diseases, WHO Pesticide Evaluation Scheme; 1997.

  3. Topical ivermectin – A Step Toward Making Head Lice Dead Lice? Chosidow O and Giraudeau B. New England Journal of Medicine, November 1, 2012. 367: 1750-1752.

  4. Single Application of 4% Dimeticone Liquid Gel Versus Two Applications of 1% Permethrin Creme Rinse for Treatment of Head Louse Infestation: A Randomized Controlled Trial. Burgess IF, Brunton ER and Burgess NA. BMC Dermatology, Vol. 13, article 5, 2013.

  5. American Academy of Pediatrics: AAP Updates Treatments for Head Lice, April 27, 2015. Accessed online at

  6. AAP Council on School Health and Committee on Infectious Diseases, Head Lice. Devore CD and Schutze GE. Pediatrics, 2015;135(5); e1355-e1365.