Published on 18/03/2015 by admin
Filed under Dermatology
Last modified 22/04/2025
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Jaime R. Gropper and Jacob O. Levitt
Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports
Lice are wingless, dorsoventrally flattened, blood-sucking insects that are obligate ectoparasites of birds and mammals. Pediculosis denotes an infestation by Pediculus capitis (head louse), Pediculus humanus (body or clothing louse), or Phthirus pubis (pubic or crab louse). The bites of lice are painless and can rarely be detected. The clinical signs and symptoms are the result of the host’s reaction to the saliva and anticoagulant injected into the dermis by the louse at the time of feeding. Depending on the degree of sensitivity and previous exposure, the feeding sites may produce red macules or papules hours to days after feeding. Pruritus is the most common symptom of any type of pediculosis. If left untreated, superinfection of excoriations may lead to impetiginous crusts and regional lymphadenopathy.
Infestation is most common among children 3–12 years of age and their parents. Identification of live lice is the gold standard of diagnosis; however, finding nits alone in a patient who has not been treated also warrants treatment. One study showed that about 20% of patients found to have nits alone go on to develop lice. Nits are easier to spot, especially at the nape of the neck and behind the ears. Hatched nits are white, unhatched nits are brown. Detection combing of wet hair with a fine-toothed nit comb allows for efficient recovery of lice and nits for diagnosis.
Management must take into consideration key elements of the head louse lifecycle. A nervous system develops in the egg by day 4, it takes 12 days at most to hatch, and the nymph can lay eggs as soon as 7 days after hatching. Contrary to the directions of most non-ovicidal pediculicides, one re-treatment at 7 days will not kill all viable nits. As such, therapies that do not kill eggs require 3 weekly treatments. Pediculicides that are also ovicidal require two treatments separated by 1 week. Ova less than 4 days old will not be affected by agents that act on the louse nervous system. Lice are sensitive to dehydration but can live off the host for up to 55 hours. Transmission is mainly by direct head to head contact. Indirect spread through fomites is also possible. Until definitive safety data are available, the occasional patient under the age of 2 years probably should be treated with mechanical methods.
Launderable items (worn clothing and used bedding, towels, scarves, and hats) should be placed in a dryer at 60°C (i.e., on high) for 10 minutes. Brushes, combs, and hair ornaments can be placed in hot (60°C or more) water for 10 minutes. Non-launderable items (i.e., certain stuffed animals) should be placed in a bag for 3 days (not 15 days, as eggs laid off a host are unlikely to hatch close enough to a host to obtain their first blood meal). Cloth furniture and rugs should be vacuumed. Fumigation of the home is discouraged.
Contacts of index cases, including classmates, should be screened. Empiric therapy for close household contacts, particularly if they share a bed, is justifiable. Those likely to have had head-to-head contact with the index case in the prior 4 to 6 weeks should be identified and screened. Children should not be excluded from school for head lice as the infestation often has been ongoing for months prior to its detection. Hair grows 1 cm per month, and lice lay eggs close to the scalp where it is moist and warm. Nits detected 2 cm from the scalp represent a 2-month-old infestation. Requiring therapy within a week of the detected infestation is more reasonable.
Considerations guiding therapy include safety and efficacy, which for chemical modalities depend largely on regional resistance patterns of the lice. Because of widespread resistance to permethrin and lindane, malathion formulated in isopropyl alcohol with terpineol, being both ovicidal and pediculicidal, was the most effective therapy at the time of the last writing and remains as such. Important new topical treatment options in light of growing resistance to treatment are benzyl alcohol lotion, spinosad topical suspension, and ivermectin lotion. Carbaryl is a good alternative but occasional resistance has been reported. Alternatives to agents that do not act on the louse nervous system include mechanical methods of louse occlusion, cuticle disruption, or physical removal. Barring shaving the head, these modalities are often unreliable and have the attendant problem of recurrent infestation occurring between treatments and continued infectiveness.
Examination for nits and lice via nit combing
Dermoscopy
Louse comb versus direct visual examination for the diagnosis of head louse infestations.
Mumcuoglu KY, Friger M, Ioffe-Uspensky I, Ben-Ishai F, Miller J. Pediatr Dermatol 2001; 18: 9–12.
Nit combing is four times more efficient and twice as fast as direct visual inspection.
Dermoscopy for diagnosis and treatment monitoring of pediculosis capitis.
Di Stefani A, Hofmann-Wellenhof R, Zalaudek I. J Am Acad Dermatol 2006; 54: 909–11.
A hand-held non-contact dermatoscope can be used to differentiate eggs containing nymphs, empty cases of hatched louses, and pseudo-nits. Treatment success can also be monitored using the dermatoscope.
The clinical trials supporting benzyl alcohol lotion 5% (Ulesfia): a safe and effective topical treatment for head lice (pediculosis humanus capitis).
Meinking TL, Villar ME, Vicaria M, Eyerdam DH, Paquet D, Mertz-Rivera K, et al. Pediatr Dermatol 2010; 27: 19–24.
Benzyl alcohol lotion 5% was studied in 695 subjects. Benzyl alcohol stuns breathing spiracles open allowing the vehicle to asphyxiate the lice. Two multicenter, randomized, double-blind, placebo-controlled trials of benzyl alcohol showed a cure rate of ~67% in 126 subjects.
Pediculosis capitis: why prefer a solution to shampoo or spray?
Armoni M, Bibi H, Schlesinger M, Pollak S, Metzker A. Pediatr Dermatol 1988; 5: 273–5.
At day 10, cure rates were 49/50 for carbaryl 0.5% lotion, 49/50 for malathion 0.5% solution, and 36/50 for pyrethrin 0.3%/piperonyl butoxide 3% shampoo.
Recent studies for carbaryl are lacking, and scattered reports of carbaryl resistance exist. As such, results of older studies may not predict efficacy today.
Sklice [package insert].
Swiftwater PA. Sanofi Pasteur Inc.; 2012.
Two identical multi-center, randomized, double-blind, vehicle-controlled studies using a single 10-minute application of ivermectin lotion without nit combing were conducted in 289 subjects aged 6 months and older, showing a cure rate of ~74%.
Therapy for head lice based on life cycle, resistance, and safety considerations.
Lebwohl M, Clark L, Levitt J. Pediatrics 2007; 119: 965–74.
This article highlights the importance of designing treatment schedules in accordance with the head lice lifecycle. Malathion 0.5% in isopropyl alcohol 78% with terpineol 12% is a safe, resistance breaking formulation approved by the FDA as a first-line treatment for head lice. Two treatments 1 week apart correlate with the head lice lifecycle. There is no evidence to suggest that the second application, 1 week later, is unsafe. 70–80% of cases are cured with a single treatment.
In the US, there is increasing resistance to permethrin and lindane but not to malathion.
Effectiveness of Ovide against malathion-resistant head lice.
Downs AM, Narayan S, Stafford KA, Coles GC. Arch Dermatol 2005; 141: 1318.
In this in vitro study, Ovide (containing malathion, terpineol, and isopropyl alcohol) killed British head lice resistant to malathion after a 60-minute exposure. Terpineol and malathion appear to be additive in overcoming resistance.
Efficacy of a reduced application time of Ovide lotion (0.5% malathion) compared to Nix creme rinse (1% permethrin) for the treatment of head lice.
Meinking TL, Vicaria M, Eyerdam DH, Villar ME, Reyna S, Suarez G. Pediatr Dermatol 2004; 21: 670–4.
Reduced application time (20 minutes) of Ovide cured 98% (40 of 41) of subjects at day 15 versus Nix (10 minutes), which cured 55% (12 of 22); 19.5% of Ovide patients and 40.9% of Nix patients required a second treatment at day 8. Re-infestation rates were 0% for Ovide and 23% for Nix.
Permethrin 1% obtained approval with well-done studies decades ago; however, resistance has caused permethrin cure rates to decline dramatically.
Increased frequency of the T929I and L932F mutations associated with knockdown resistance in permethrin-resistant populations of the human head louse, Pediculus capitis, from California, Florida and Texas.
Gao JR, Yoon KS, Lee SH, et al. Pestic Biochem Physiol 2003; 77: 115–24.
A high prevalence of kdr (knock-down resistance) gene mutations in head lice is reported: 45% in California, 87% in Florida, and up to 100% in parts of Texas. The kdr gene decreases louse voltage-gated sodium channel affinity for permethrin, rendering it ineffective.
Efficacy and safety of spinosad and permethrin creme rinses for pediculosis capitis (head lice).
Stough D, Shellabarger S, Quiring J, Gabrielsen AA Jr. Pediatrics 2009; 124: 389–95.
Two phase III, multicenter, randomized, evaluator/investigator-blinded studies compared 0.9% spinosad without nit-combing to 1% permethrin with combing in 1038 subjects aged ≥6 months. The efficacy of spinosad (~86%) was statistically superior to permethrin (~44%). Spinosad did not require a combing step, and most patients required one rather than two applications.
Spinosad was more effective than permethrin, the currently recommended first-line treatment by the American Academy of Pediatrics.
A single application of crotamiton lotion in the treatment of patients with pediculosis capitis.
Karaci I, Yawalkar SJ. Int J Dermatol 1982; 21: 611–13.
Forty-seven of 49 subjects were cured with one application of crotamiton 10% lotion, and all were cured with a second application at 1 week. The trial was open-label and never independently validated.
A randomised, assessor blind, parallel group comparative efficacy trial of three products for the treatment of head lice in children – melaleuca oil and lavender oil, pyrethrins and piperonyl butoxide, and a ‘suffocation’ product.
Barker SC, Altman PM. BMC Dermatol 2010; 10: 6.
This study compared three products. Cure rates were as follows: malaleuca (tea tree) oil and lavender oil (41/42; 98%); NeutraLice, a suffocation product (40/41; 98%); products containing pyrethrins and piperonyl butoxide (10/40; 25%).
A randomized, assessor-blind, parallel-group, multicentre, phase IV comparative trial of a suffocant compared with malathion in the treatment of head lice in children.
Greive KA, Lui AH, Barnes TM, Oppenheim VM. Australas J Dermatol 2010; 51: 175–82.
In a study of 216 Australian children, a commercially available suffocant (MOOV Head Lice Sensitive) was shown to be significantly more effective in eliminating head lice than a malathion containing foam in children, while being associated with a low incidence of mild, transient adverse events.
Treatment of head louse infestation with 4% dimethicone lotion: randomised controlled equivalence trial.
Burgess IF, Brown CM, Lee PN. BMJ 2005; 330(7505): 1423.
Cure rates of 70% after 2 weekly 8-hour treatments in 253 subjects were achieved.
This therapy does not appear to be ovicidal, perhaps contributing to a lower cure rate.
A simple treatment for head lice: dry-on, suffocation-based pediculicide.
Pearlman DL. Pediatrics 2004; 114: e275–9.
Cetaphil cleanser is applied to the hair, dried with a hair dryer, followed by nit combing for three times separated by 1 week. A total of 133 patients were studied; 96% efficacy is claimed. The study was open-label, and the results were never independently validated.
North American efficacy and safety of a novel pediculicide rinse, isopropyl myristate 50% (Resultz).
Kaul N, Palma KG, Silagy SS, Goodman JJ, Toole J. J Cutan Med Surg 2007; 11: 161–7.
In the isopropyl myristate (IPM) arm of one small, randomized trial, 18 of 30 subjects were cured at 21 days by an intention to treat analysis. IPM is thought to dissolve the waxy coat of the louse exoskeleton, causing fatal dehydration of the louse. As the louse eggshell is proteinaceous, this chemical is not expected to kill eggs.
Single blind, randomised, comparative study of the Bug Buster kit and over the counter pediculicide treatments against head lice in the United Kingdom.
Hill N, Moor G, Cameron MM, Butlin A, Preston S, Williamson MS, et al. Br Med J 2005; 331(7513): 384–7.
A cure rate of 57% (32/56) is reported for wet combing with conditioner in four sessions over 13 days.
Nit combing can be painful and time-consuming but may be worthwhile where lice are resistant to pharmacotherapy.
Treatment of pediculosis capitis with topical albendazole.
Ayoub N, Maatouk I, Merhy M, Tomb R. J Dermatolog Treat 2012; 23: 78–80.
Four patients with head lice were successfully treated with topical albendazole 2% suspension.
Home remedies to control head lice: assessment of home remedies to control the human head louse, Pediculus humanus capitis (Anoplura: Pediculidae).
Takano-Lee M, Edman JD, Mullens BA, Clark JM. J Pediatr Nurs 2004; 19: 393–8.
‘Home remedies’ (vinegar, isopropyl alcohol, olive oil, mayonnaise, and melted butter) are, in general, neither pediculicidal nor ovicidal. Petroleum jelly was 62% pediculicidal and 94% ovicidal. The need for 8 hours of water submersion to achieve significant lice mortality makes water submersion impractical.
While not addressed in this reference, topically applied kerosene is a dangerous method that should be avoided.
Oral ivermectin versus malathion lotion for difficult-to-treat head lice.
Chosidow O, Giraudeau B, Cottrell J, Izri A, Hofmann R, Mann SG, et al. N Engl J Med 2010; 362: 896–905.
This multicenter, cluster-randomized, double-blind, double-dummy, controlled trial in 812 patients compared oral ivermectin (at a dose of 400 µg/kg body weight) with 0.5% malathion lotion, each given on days 1 and 8. Included were subjects who had live lice not eradicated by topical insecticide used 2 to 6 weeks before enrollment. In the intention-to-treat population, 95.2% of patients receiving ivermectin were lice-free on day 15, as compared with 85.0% of those receiving malathion.
Oral ivermectin, given twice at a 7-day interval, had superior efficacy as compared with topical 0.5% malathion lotion with no increased side effects. Safety studies of oral ivermectin in children are lacking.
Comparative in vitro pediculicidal efficacy of treatments in a resistant head lice population in the United States.
Meinking TL, Serrano BA, Hard B, Entzel R, Lemard G, Rivera E, et al. Arch Dermatol 2002; 138: 220–4.
Lindane shampoo was the slowest and the least effective product, killing only 8% of lice in 1 hour. It is labeled for 4 minutes application time.
Lindane toxicity: a comprehensive review of the medical literature.
Nolan K, Kamrath J, Levitt J. Pediatr Dermatol 2012; 29: 141–6.
Lindane has been associated with significant adverse reactions, including death, seizures, shortness of breath, and hematologic effects. Lindane has been banned in some US states, including California and Michigan. It is no longer recommended for use in children younger than 10 years, those weighing less than 50 kg, breastfeeding women, older adults, or people with compromised dermal barriers.
Given the significant toxicity associated with lindane and the availability of multiple other safer treatments, lindane should be avoided.
Head lice infestation: single drug versus combination therapy with one percent permethrin and trimethoprim/sulfamethoxazole.
Hipolito RB, Mallorca FG, Zuniga-Macaraiq ZO, Apolinario PC, Wheeler-Sherman J. Pediatrics 2001; 107: E30.
Permethrin (1%) and trimethoprim (10 mg/kg/day divided bid)/sulfamethoxazole (TMP/SMX) cured 38 of 40 (95%) of subjects at week 2. TMP/SMX monotherapy was 83% effective, and permethrin monotherapy was 79.5% effective.
Levamisole: a safe and economical weapon against pediculosis.
Namazi MR. Int J Dermatol 2001; 40: 292–4.
Levamisole in a dose of 3.5 mg/kg administered open-label for 10 days cured 67% (18/28) of children with head lice.
As body lice live in the seams of clothing, treatment revolves around laundering of clothing and bedding in high heat (>60°C) for at least 10 minutes. Infested mattresses should be abandoned for 3 weeks. Given that resistance patterns in head lice follow those of body lice, topical malathion, carbaryl, or permethrin are good first choices. Oral ivermectin is another alternative. All household contacts should be treated. Monitor for symptoms of louse-borne illness, specifically epidemic typhus (Rickettsia prowazekii), relapsing fever (Borrelia recurrentis), and trench fever (Bartonella quintana).
Human lice and their management.
Burgess IF. Adv Parasitol 1995; 36: 271–342.
A comprehensive review of human lice is provided. For body lice, laundering of clothing is stressed, and the use of pediculicides on the patient is questioned. In mass eradication, fomites can be dusted with malathion or permethrin.
Given the safety of topical therapy, two treatments applied for 8 to 12 hours 1 week apart outweigh the risk of stray lice on the host re-establishing infestation.
Crab lice commonly affect pubic (mons and perianal), thigh, chest, and axillary hair, eyelashes, and, rarely, scalp hair. Pediculicide should be applied to these areas to ensure irradication. Eyelash infestation should be treated separately (see below). Household contacts and sexual partners of the prior month should be treated. Fomites should be laundered as for head lice. Screening for other sexually transmitted diseases is advised.
Infestations.
Meinking TL. Curr Probl Dermatol 1999; 11: 73–120.
A comprehensive review of pediculosis and scabies is rendered. The lifecycle of the crab louse mirrors that of the head louse, such that therapeutic strategies are analogous. Successful treatment using two applications separated by 1 week to the entire body was achieved in 27 of 28 (96%) patients with permethrin 1% crème rinse and 24 of 29 (83%) patients with lindane 1%. Meinking reports a separate study where a single total-body application of permethrin 5% cream yielded a 93% cure rate (number of patients not reported); however, single application therapy is too often ineffective to recommend.
Only anecdotal reports of therapy exist. Alcoholic formulations as well as lindane are ocular irritants and should be avoided. Physostigmine is effective but may inhibit dark adaptation of the eye. Petrolatum application or mechanical removal of lice and nits seem to be the safest alternatives. Treatment of household and sexual contacts and fomites is warranted.
Pediculosis ciliaris.
Chin GN, Denslow GT. J Pediatr Ophthalmol Strabismus 1978; 15: 173–5.
Physotigmine 1% ointment applied to eyelid margins twice a day for 14 days is reported. Other suggestions for therapy include: (1) thick application of petroleum jelly bid for 8 days; (2) mechanical removal of lice and nits with forceps and cotton-tipped swabs followed by application of yellow oxide of mercury 1–2% ointment twice a day for 1 week; or (3) cryotherapy.
Oral ivermectin therapy for phthiriasis palpebrum.
Burkhart CN, Burkhart CG. Arch Ophthalmol 2000; 118: 134–5.
A single case of oral ivermectin use in lash pediculosis.
Argon laser phototherapy of phthiriasis palpebrarum.
Awan KJ. Ophthalmic Surg 1986; 17: 813–14.
Argon laser phototherapy was employed to treat phthiriasis palpebrarum in one sitting. A beam at a setting of 200 µm size, 0.1 second time, and 200 mW power was employed to destroy individual adult parasites and nits.
Treatment of Skin Disease Comprehensive Therapeutic Strategies 4e
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