Lice and Scabies: Treatment Update

 

Am Fam Physician. 2019 May 15;99(10):635-642.

  Patient information: See related handout on lice and scabies, written by the authors of this article.

Author disclosure: No relevant financial affiliations.

Pediculosis and scabies are caused by ectoparasites. Pruritus is the most common presenting symptom. Head and pubic lice infestations are diagnosed with visualization of live lice. Nits (lice eggs or egg casings) alone are not sufficient to diagnose a current infestation. A “no-nit” policy for return to school is not recommended because nits can remain even after successful treatment. First-line pharmacologic treatment for pediculosis is permethrin 1% lotion or shampoo. Newer treatments are available but costly, and resistance patterns are generally unknown. Noninsecticidal agents, including dimethicone and isopropyl myristate, show promise in the treatment of pediculosis. Extensive environmental decontamination is not necessary after pediculosis is diagnosed. In adults, the presence of pubic lice should prompt an evaluation for sexually transmitted infections. Body lice infestation should be suspected in patients with pruritus who live in crowded conditions or have poor hygiene. Scabies in adults presents as a pruritic, papular rash in a typical distribution pattern. In infants, the rash can also be vesicular, pustular, or nodular. First-line treatment for scabies is permethrin 5% cream. Clothing and bedding of persons with scabies should be washed in hot water and dried in a hot dryer. Counseling regarding appropriate diagnosis and correct use of effective therapies is key to reducing the burden of lice and scabies.

Pediculosis and scabies are caused by ectoparasites. Pruritus is the most common presenting symptom with both conditions. Determining the specific etiology of pruritus based on history and physical examination findings is important. Lice in particular may be overdiagnosed by anxious patients and treated using over-the-counter medications without an office evaluation.1 Seeking an appropriate clinical diagnosis may help reduce treatment-resistant lice. Although the diagnosis of pediculosis and scabies has not changed substantially, there are new developments in treatment since this topic was previously covered in American Family Physician.24

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SORT: KEY RECOMMENDATIONS FOR PRACTICE

Clinical recommendationEvidence ratingReferencesComment

A “no-nit” policy is not recommended for schools and day cares because nits alone do not indicate an active infestation. Children should not be kept out of school during treatment, even with active infestation, because the likelihood of transmission is low, and this can result in significant absences.

C

1, 8

U.S. and Canadian consensus guidelines based on basic knowledge of the lice life cycle

Permethrin 1% lotion or shampoo (Nix) is first-line treatment for pediculosis. Alternative treatments should not be used unless permethrin fails after two treatments.

C

1, 8

U.S. consensus guidelines balancing effectiveness and toxicity

Nonovicidal therapies for pediculosis should be applied twice, seven to 10 days apart, to fully eradicate lice. Some authors postulate that three treatments with permethrin or pyrethrins might be most effective.

C

1, 8, 19, 20

U.S. and Canadian consensus guidelines based on basic knowledge of the lice life cycle Inappropriate retreatment may result in resistance and lack of treatment effectiveness

Scabies should be considered in patients with a pruritic, papular rash in the typical distribution and pruritus in close contacts. The classic burrows in webs and creases may not be present.

C

27, 2931

U.S. and European consensus guidelines based on epidemiologic data and case studies

Oral ivermectin (Stromectol) should be reserved for patients with scabies who do not improve with permethrin 5% cream (Elimite).

C

10, 31

Guidelines using consensus agreement in area of little clinical research


A = consistent, good-quality patient-oriented evidence; B = inconsistent or limited-quality patient-oriented evidence; C = consensus, disease-oriented evidence, usual practice, expert opinion, or case series. For information about the SORT evidence rating system, go to https://www.aafp.org/afpsort.

SORT: KEY RECOMMENDATIONS FOR PRACTICE

Clinical recommendationEvidence ratingReferencesComment

A “no-nit” policy is not recommended for schools and day cares because nits alone do not indicate an active infestation. Children should not be kept out of school during treatment, even with active infestation, because the likelihood of transmission is low, and this can result in significant absences.

C

1, 8

U.S. and Canadian consensus guidelines based on basic knowledge of the lice life cycle

Permethrin 1% lotion or shampoo (Nix) is first-line treatment for pediculosis. Alternative treatments should not be used unless permethrin fails after two treatments.

C

1, 8

U.S. consensus guidelines balancing effectiveness and toxicity

Nonovicidal therapies for pediculosis should be applied twice, seven to 10 days apart, to fully eradicate lice. Some authors postulate that three treatments

The Authors

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KAREN GUNNING, PharmD, is a professor of pharmacotherapy at the University of Utah College of Pharmacy and an adjunct professor in the Department of Family and Preventive Medicine at the University of Utah School of Medicine in Salt Lake City....

BERNADETTE KIRALY, MD, is an associate professor in the Department of Family and Preventive Medicine at the University of Utah School of Medicine.

KARLY PIPPITT, MD, is an associate professor in the Department of Family and Preventive Medicine at the University of Utah School of Medicine.

Address correspondence to Karen Gunning, PharmD, University of Utah, 30 South 2000 East, Rm. 4982, Salt Lake City, UT 84112 (e-mail: karen.gunning@hsc.utah.edu). Reprints are not available from the authors.

Author disclosure: No relevant financial affiliations.

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