Lice and Scabies: Treatment Update

Karen Gunning, PharmD; Bernadette Kiraly, MD; Karly Pippitt, MD

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

Clinical Presentation

Persons with scabies typically present with intense, generalized pruritus that is worse at night. The face and neck are unaffected. The primary skin lesions are erythematous, pruritic papules, pustules, vesicles, and nodules. The pathognomonic finding is a burrow (Figure 4), which is not always evident. The lesions are most commonly found on the finger webs, wrist flexors, elbows, axillae, buttocks, genitalia, and breasts.^[25,26] Nonspecific secondary skin findings may include excoriations, eczematization, and pyoderma. The characteristic distribution of lesions in adults with scabies is illustrated in Figure 5.^[3] Infants may present with pustules on the palms and soles and vesicles or other lesions on the neck and face.^[25,26]

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Figure 4.

Erythematous papules and burrows typical of scabies.
Image used with permission from VisualDx.

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Figure 5.

Characteristic distribution of lesions in adults with classic scabies. Burrows are more common on hands and wrists, whereas papular or nodular lesions are generally present elsewhere.
Reprinted with permission from Flinders DC, De Schweinitz P. Pediculosis and scabies. Am Fam Physician. 2004;69(2):345.

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Table 1. Pharmacologic Treatments for Head Lice
Treatment	Ovicidal?	Mechanism of action	Directions (per package inserts)	Effectiveness	Cost*	Comments
Benzyl alcohol 5% lotion (Ulesfia); prescription	No	Suffocation	Apply to dry hair, leave on for 10 minutes then rinse; repeat in seven days	75% to 76% of patients are lice free at 14 days¹¹	— ($450) for two bottles	Can be costly for long hair (dosing is based on hair length) Must be used in conjunction with a lice comb (also called nit comb) Approved for persons six months and older, may be used in pregnant and lactating women
Dimethicone solution (Nix Ultra, Lice MD); OTC	No	Suffocation	Spray all over dry hair, and massage until wet; let it sit for 30 minutes, then comb into hair; leave on overnight; wash out, and use a lice comb; repeat in eight to 10 days	70% to 96% of patients are lice free at 14 days (study of dimethicone 100%)^12,13	— ($10 to $20) for one bottle	May cause eye irritation Should not be used in children younger than two years
Isopropyl myristate (Resultz); OTC†	No	Exoskeleton dissolution	Apply to dry hair and scalp, leave on for 10 minutes then rinse with warm water; repeat in eight to 10 days	54% to 82% of patients are lice free at 14 to 21 days¹²	—	May cause local and eye irritation Not recommended for children younger than four years
Ivermectin 0.5% lotion (Sklice); prescription	Not directly, but lice hatched from treated eggs die within 48 hours	Neurotoxic to lice⁴	Apply to dry hair and scalp, leave on for 10 minutes then rinse; one application is sufficient	74% of patients are lice free at 15 days¹⁴	— ($360) for one tube	Rare adverse effects include skin and eye irritation, erythema, burning, dryness
Ivermectin, oral (Stromectol); prescription‡	Partial	Neurotoxic to lice	200 mcg per kg, two doses seven to 10 days apart⁸	92% to 97% of patients are lice free at 14 to 15 days after two doses¹⁵	$5 ($8) for one 3-mg tablet (dosing varies based on weight)	Do not use in children weighing less than 33 lb (15 kg) or in pregnant women
Malathion 0.5% lotion (Ovide); prescription	Partial	Neurotoxic to lice	Apply to dry hair until hair and scalp are wet, allow to dry naturally, shampoo eight to 12 hours later, rinse and use a lice comb; repeat after seven to nine days only if live lice are still present	80% of patients are lice free at 14 days¹⁶	$150 ($270) for one bottle	Flammable; do not use with a hair dryer or near cigarettes or an open flame
Permethrin 1% shampoo (Nix); OTC	No	Neurotoxic to lice	Apply to damp hair, leave on for 10 minutes then rinse; repeat in seven days	50% to 97% of patients are lice free at 14 days^1,8,17	$20 for two treatments	First-line treatment¹
Pyrethrins 0.3%/piperonyl butoxide 4% shampoo or mousse (Rid); OTC	No	Neurotoxic to lice	Apply to dry hair, leave on for 10 minutes then rinse; repeat in seven days	62% to 94% of patients are lice free (unclear time frame)¹	— ($15 to $20) for two treatments	Piperonyl butoxide is thought to prolong the activity of pyrethrins Avoid in patients with chrysanthemum allergy
Spinosad 0.9% suspension (Natroba); prescription	Yes	Neurotoxic to lice	Apply to dry hair, leave on for 10 minutes then rinse; repeat in seven days only if live lice are present	68% to 87% of patients are lice free at 14 days¹⁶	$200 ($280) for one bottle	May be used without a lice comb, although use of a lice comb improves results Safe for use in children four years and older Do not use in infants younger than six months because it contains benzyl alcohol

FDA = U.S. Food and Drug Administration; OTC = over the counter.
*—Estimated retail price based on information obtained at https://www.goodrx.com (accessed October 22, 2018) and Walgreens. Generic price listed first; brand name price listed in parentheses.
†—FDA approved in May 2017 but not yet marketed in the United States.
‡—Off-label use.
Adapted with permission from Gunning K, Pippitt K, Kiraly B, Sayler M. Pediculosis and scabies: treatment update. Am Fam Physician. 2012;86(6):537, with additional information from references 1, 4, 8, and 11through 17.

Table 2. Differential Diagnosis of Scabies
Contact dermatitis
Eczema
Folliculitis
Impetigo
Insect bites (mosquitoes, fleas, bedbugs)
Irritant dermatitis
Tinea

Information from references 5 and 32.

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Sort: Key Recommendations for Practice

Clinical recommendation	Evidence rating	References	Comment
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, 29–31	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.