Head lice infestations: A clinical update
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Head lice (Pediculus humanus capitis) infestations remain a pesky communicable problem, particularly in school-age children in Canada and elsewhere (1,2). A small 2003population-based study (3) of primary school children in theUnited Kingdom noted a 2% prevalence and a 37% annualincidence of head lice.
Unlike body lice, head lice are not a health hazard, a sign of poor hygiene or a vector for disease, but are more a soci-etal issue (2).
The present statement updates the 2004 statement (4), and highlights changes in head lice treatment products Figure 1) An adult louse measures 2 mm to 4 mm in length.
available in Canada, reports treatment failures, and reviews Reproduced with permission from reference 31 recent studies that provide evidence and rationale for man-agement recommendations.
Head lice are spread mainly through direct head-to-head Head lice are wingless, 2 mm to 4 mm long (adult louse), six- (hair-to-hair) contact (10,11). Lice do not hop or fly, but legged, blood-sucking insects that live on the scalp of can crawl at a rapid rate (23 cm/min under natural condi- humans (5). Infested children usually carry fewer than tions) (9). There continues to be controversy about the role 20 mature head lice (more commonly, less than 10 head lice), fomites play in transmission (9). Two studies from Australia each of which, if untreated, live for three to four weeks (6-8).
suggest that in the home, pillowcases present only a small Head lice stay close to the scalp for food, warmth, shelter and risk (1), and in the classroom, the carpets pose no risk (12).
moisture (7,8). The head louse feeds every 3 h to 6 h by suck- Pets are not vectors for human head lice (3).
ing blood and simultaneously injecting saliva. After mating,the adult female louse can produce five to six eggs per day for DIAGNOSIS
30 days (9), each in a shell (a nit) that is ‘glued’ to the hair The definitive diagnosis of head lice infestation requires the shaft near the scalp (6,7). The eggs hatch nine to 10 days later detection of a living louse (2,7,10) (Figure 1). The presence into nymphs that molt several times over the next nine to of nits indicate a past infestation that may not be currently 15 days to become adult head lice (6). The hatched empty eggshells (nits) remain on the hair, but are not a source of Because head lice can move quickly, their detection reinfestation. Nymphs and adult head lice can survive for up requires expertise and experience. An Israeli study (13) with to three days away from the human host (9). While eggs can experienced parasitologists noted that combing with a fine- survive away from the host for up to three days, they require toothed lice comb was four times more effective and twice as the higher temperature found near the scalp to hatch (8).
fast as direct visual examination for the detection of live headlice, and hence, for the diagnosis of head lice infestations.
Pollack et al (14) also found that expertise is key to diag- An infestation with lice is called pediculosis, and usually nosis. They documented that health care providers and lay involves less than 10 live lice (8). Itching occurs if the indi- personnel frequently overdiagnosed and misdiagnosed vidual becomes sensitized to antigenic components of louse pediculosis (14). Many failed to distinguish active from saliva that is injected as the louse feeds (2,8). On the first extinct infestations, particularly if they were relying only on infestation, sensitization commonly takes four to six weeks nit detection. School nurses were particularly adept at spot- (8,10). However, some individuals remain asymptomatic and ting nits, but appeared to lack the expertise, equipment, never itch (8). In cases with heavy infestations, secondary time and inclination to distinguish active from inactive bacterial infection of the excoriated scalp may occur. Unlike infestations. A viable nit is more likely to be found close to body lice, head lice are not vectors for other diseases (8,10).
the scalp (less than 0.6 cm away) (15). On microscopy, a Correspondence: Canadian Paediatric Society, 2305 St Laurent Boulevard, Ottawa, Ontario K1G 4J8. Telephone 613-526-9397, fax 613-526-3332, Web sites www.cps.ca, www.caringforkids.cps.ca 2008 Canadian Paediatric Society. All rights reserved Paediatr Child Health Vol 13 No 8 October 2008 CPS Statement: ID 2008-06
Topical treatments of head lice infestations

Trade name
Active ingredient
Method of use in brief
Areas of concern
Resistance documented R&C Shampoo + Pyrethrin plus • Apply to dry hair that does not have Made from natural extracts • Soak with minimum of 25 mL • Rinse well with cool water, minimizing Permethrin
Resistance documented Kwellada-P Creme 1% permethrin • After washing hair with conditioner-free • Does not cause Argentina, France, Israel, Nix Creme Rinse‡ Neurotoxic to lice, but • Rinse well with cool water, minimizing • Rub shampoo into hair and scalp, allow Noninsecticide
exoskeleton of the louse, • Thoroughly apply to dry hair and scalp • 30 mL to 60 mL for short hair, 60 mL to • Rinse off with warm water • Repeat in 7 days *GlaxoSmithKline Consumer Healthcare, Canada; †Itching and burning sensation of the scalp, which occurs following treatment, does not necessarily indicate rein-festation and need for retreatment. If bothersome, topical steroids and antihistamines may be helpful (9); ‡Insight Pharmaceuticals, Canada; §Odan LaboratoriesLtd, Canada; ¶Pharmascience Inc, Canada (according to the Compendium of Pharmaceuticals and Specialties 2000. Ottawa: Canadian Pharmacists Association,2000); **Nycomed Canada Inc. DDT Dichlorodiphenyltrichloroethane Paediatr Child Health Vol 13 No 8 October 2008 CPS Statement: ID 2008-06
viable nit can be seen as intact and containing a well- is not recommended for use in infants, young children, hydrated mass or a discernibly developing embryo (14).
pregnant and nursing mothers (17). Special care should be However, without the ability to distinguish potentially viable taken to ensure that the package directions are carefully fol- from nonviable nits, conclusions on the potential for active lowed. On an additional note, pharmaceutical use of lin- infestation by nit detection alone are not reliable (14).
dane has been banned in California since 2002 based on Finding nits close to the scalp is, at best, only a modest concerns about contamination of waste water with lindane.
predictor of possible active infestation. While a study in A follow-up study of waste water from California published Georgia, USA (15), found that having five or more nits in 2008 showed a marked reduction of lindane levels com- within 0.6 cm of the scalp was a risk factor for becoming pared with levels before the ban (18).
infested with active lice, this occurred in fewer than 32% of Resistance to topical insecticides: Resistance has been
such children (15). For children with fewer than five nits reported with pyrethrins, permethrin and lindane in a num- close to the scalp, only 7% became actively infested. Hence, ber of countries (Table 1) (6,19). While some resistance to having nits close to the scalp does not necessarily indicate permethrin has been documented in the United States, that a live lice infestation has occurred or will occur. resistance to other topical agents has not been proven (20).
In the United Kingdom, resistance can be a problem (2,21).
The resistance rates in Canada are unknown because formal Well-established treatment options for proven head lice studies have not been performed. A number of other diag- infestation, include topical insecticides, oral agents and wet noses should be ruled out before resistance is considered combing. A new noninsecticidal product has recently been • misdiagnosis and overdiagnosis (diagnosis requires Topical insecticides
detection of live lice before treatment); Table 1 presents a list of the topical insecticides (pyrethrins, • poor compliance with instructions for proper permethrin 1% and lindane) currently available for the application of the topical insecticide, lack of secondary treatment of head lice infestations in Canada, their active application or reapplication too soon after first ingredients, methods of use and areas of concern.
Malathion lotion (0.5%) and crotamiton lotion (10%) arenot available in Canada.
• new infestation acquired after treatment. The most recent Cochrane review (16) noted that only Of particular note, itching occurring post-treatment three studies of treatment of head lice with topical insec- with a topical insecticide does NOT mean that a reinfesta- ticides met appropriate inclusion criteria (two placebo- tion has occurred. Application of an approved topical controlled studies and one comparative clinical field insecticide to the scalp can cause rash, itching and mild study). On the basis of these three trials, the review con- burning (6). The diagnosis of a reinfestation requires the cluded that permethrin, malathion and synergized detection of live lice. If the post-treatment itching is both- pyrethrins (ie, pyrethrin with piperonyl butoxide) proved ersome, topical steroids and/or antihistamines may help to None of these three topical insecticides (pyrethrin, per- methrin and lindane) are 100% ovicidal; thus, reapplica- Oral agents
tion seven to 10 days later is generally recommended (10).
Data to support the use of oral agents for the treatment of Toxicity of topical insecticides: Both pyrethrins and per-
methrin have favourable safety profiles with minimal percu- Although trimethoprim-sulfamethoxazole has been taneous absorption (6). To minimize body exposure to a used in a randomized trial (22) to treat head lice, both topical insecticide following application to the scalp, rinse alone and in combination with topical permethrin, con- well using cool water taking care to avoid unnecessary skin cerns have been raised about the diagnostic criteria used exposure to the product – do not sit the child in the bath in the trial and the potential for promoting bacterial resistance and further reducing the value of this drug in Lindane is considered to be a second-line therapy other settings if this practice becomes widespread (20).
because of the potential for neurotoxicity and bone marrow There are no published large trials. This is not an suppression following percutaneous absorption (6,17). The approved use of trimethoprim-sulfamethoxazole in Food and Drug Administration (17) has issued an advisory concerning the use of lindane-containing products for the There are reports (2) regarding the oral (and topical) treatment of lice and scabies. Neurological side effects have use of ivermectin, an antihelminthic agent for the treat- been reported in patients using lindane correctly, although ment of head lice. Treatment consists of two single oral most serious outcomes, including death and hospitaliza- doses, 200 µg/kg spaced seven to 10 days apart. Ivermectin tions, occurred after multiple applications or oral ingestion.
is potentially neurotoxic and should not be used in chil- A safe interval for the reapplication of lindane has not been dren who weigh less than 15 kg (10). This drug is available established (17). Topical lindane for treatment of head lice in Canada only through special access programs (23).
Paediatr Child Health Vol 13 No 8 October 2008 CPS Statement: ID 2008-06
Wet combing
and close head-to-head contact should be discouraged pend- There is little evidence in support of wet combing as a primary ing treatment. The American Academy of Pediatrics and the treatment for head lice (24,25). In a randomized trial of Public Health Medicine Environmental Group in the United 4037 school children in Wales, United Kingdom (24), Kingdom also discourage ‘no nit’ school policies (2,9).
mechanical removal of lice through combing of wet hair with Families of children in the classroom where a case of a fine-toothed comb every three to four days for two weeks active head lice has been detected should be alerted that an was compared with two applications of topical 0.5% active infestation has been noted, and informed about the malathion lotion seven days apart (24). Wet combing resulted diagnosis, misdiagnosis and management of head lice, and in a cure (no detection of live lice after two weeks) in 38%, the lack of risk for serious disease.
while the malathion treatment resulted in a cure in 78% (24).
In another study (24), the addition of wet combing to the top- ROLE OF ENVIRONMENTAL
ical 1% permethrin treatment protocol did not improve the DECONTAMINATION
efficacy of permethrin treatment alone when assessed at days Data on whether disinfection of personal, school or house- 2, 8, 9 and 15 (combing 72.7%, no combing 78.3%). While hold items decreases the likelihood of reinfestation are vinegar has been suggested as a home remedy to aid wet lacking (11,12). As noted, head lice do not live far away combing, there are no studies showing its benefit.
from the scalp, and nits are unlikely to hatch at room tem-perature (8,9). Hence, excessive cleaning is not warranted.
Other treatments
At most, the cleaning of items in prolonged or intimate Health Canada has recently approved the use of a new non- contact with the head (eg, hats, pillowcases, brushes and insecticidal product containing isopropyl myristate 50% and combs) may be warranted. Washing the item in hot water ST-cyclomethicone 50% (Resultz, Nycomed Canada Inc) for (66°C), drying it in a hot dryer for 15 min or storing it in an the treatment of head lice in children four years of age and occlusive plastic bag for two weeks will kill lice and nits older. The agent works by dissolving the waxy exoskeleton of the louse, leading to dehydration and death. The product isapplied to a dry scalp, and rinsed off in 10 min. This product ROLE OF HEALTH CARE PROVIDERS
is not ovicidal, and thus a second application in one week is Given the prevalence of infestations, the notoriety and recommended. Several small phase II trials (200 to 300 par- high anxiety levels that a diagnosis of head lice in school ticipants only) have demonstrated efficacy and minimal side children can generate in parents and/or teachers, health effects, the most common being mild erythema and pruritis care providers need to ensure that head lice myths are dis- of the scalp (26-29). Phase III trials are ongoing. pelled and that accurate information is provided (2).
A number of household products, such as mayonnaise, Parents and teachers need to be informed that head lice petroleum jelly, olive oil, tub margarine and thick hair gel, infestations are common, may be asymptomatic, are not a have been suggested as treatment for head lice. Application sign of uncleanliness and are not a vector for serious med- of a thick coating of such agents to the hair and scalp left on ical diseases. Information on optimizing diagnosis and min- overnight will theoretically occlude lice spiracles and imizing misdiagnosis, and appropriate management decrease respiration (6). However, these products show lit- strategies if a case is diagnosed, need to be provided.
tle killing of lice and are less effective than topical insecti-cides (8). There are no published trials on the safety or • Head lice infestations are common in school children Other products such as gasoline or kerosene are flamma- but are not associated with serious disease and are not While a number of ‘natural’ agents, such as tea tree oil and aromatherapy, have been used for the treatment of • Head lice infestations can be asymptomatic for weeks.
head lice, efficacy and toxicity data are not available for • Misdiagnosis of head lice infestations is common. The these agents (7,8). One small study in Israel (30) noted that diagnosis requires detection of live head lice. Detection a natural product, which contained coconut oil, anise oil of nits alone does not indicate active infestation.
and ylang ylang oil, applied to hair three times at five-dayintervals, was as successful as the control pediculicide.
• Treatment with an approved, properly applied, topical Products intended for treating lice in animals are not head lice insecticide (two applications seven to 10 days apart) is recommended when a case of activeinfestation is detected. Contacts of cases in which SCHOOL AND DAYCARE HEAD LICE
head-to-head touching may have occurred merit AND NIT POLICIES
examination to detect active infestation and, if Exclusion from school and daycare due to the detection of the presence of ‘nits’ does not have sound medical rationale. Even • Scalp itchiness can occur following application of a the detection of active head lice should not lead to the exclu- topical insecticide and does not indicate that sion of the affected child. Treatment should be recommended resistance to treatment or a reinfestation has occurred.
Paediatr Child Health Vol 13 No 8 October 2008 CPS Statement: ID 2008-06
Diagnosis of an active reinfestation requires detection 13. Mumcuoglu KY, Friger M, Ioffe-Uspensky I, Ben-Ishai F, Miller J.
Louse comb versus direct visual examination for the diagnosis ofhead louse infestations. Pediatr Dermatol 2001;18:9-12. • Topical insecticides, especially lindane, can be toxic, 14. Pollack RJ, Kiszewski AE, Spielman A. Overdiagnosis and consequent mismanagement of head louse infestations in North particularly if misused. Care should be taken to avoid America. Pediatr Infect Dis J 2000;19:689-93. unnecessary exposure and, when indicated, to 15. Williams LK, Reichert MA, MacKenzie WR, Hightower AW, minimize skin contact beyond the scalp.
Blake PA. Lice, nits and school policy. Pediatrics 2001;107:1011-5. 16. Dodd CS. Interventions for treating headlice (Cochrane review).
• ‘No nit’ school exclusion policies lack a rational Cochrane Database Syst Rev 2001;3:CD001165. 17. Centre for Drug Evaluation and Research. FDA public health medical basis and are not recommended.
advisory: Safety of topical lindane products for the treatment ofscabies and lice. <www.fda.gov/cder/drug/infopage/ • Excessive household or school cleaning is not lindane/lindanePHA.htm> (Version current at May 21, 2008).
warranted following the detection of a case of head 18. Humphreys EH, Janssen S, Heil A, Hiatt P, Solomon G, Miller MD.
lice because neither head lice nor nits survive for an Outcomes of the California ban on pharmaceutical lindane: Clinicaland ecologic impacts. Environ Health Perspect 2008;116:297-302.
extended period of time away from the scalp.
19. Pollack RJ, Kiszewski A, Armstrong P, et al. Differential permethrin susceptibility of head lice sampled in the United States • While resistance to topical agents has been noted in and Borneo. Arch Pediatr Adolesc Med 1999;153:969-73. other countries, this does not appear to be as large a 20. Pollack RJ. Head lice infestations: Single drug versus combination 21. Downs AM. Managing head lice in an era of increasing resistance to insecticides. Am J Clin Dermatol 2004;5:169-177.
22. Hipolito RB, Mallorca FG, Zuniga-Macaraig ZO, Apolinario PC, 1. Gratz NG. Human lice: Their prevalence, control and resistance Wheeler-Sherman J. Head lice infestations: Single drug versus to insecticides: A review 1985-1997. Geneva: World Health combination therapy with one percent permethrin and Organization, 1997. <whqlibdoc.who.int/hq/1997/WHO_CTD_ trimethoprim/sulfamethoxazole. Pediatrics 2001;107:E30.
WHOPES_97.8.pdf> (Version current at August 20, 2008).
23. Health Canada. Drugs and health products. 2. Public Health Medicine Environmental Group. Head lice: Evidence- <http://www.hc-sc.gc.ca/dhp-mps/acces/drugs-drogues/ based guidelines based on the Stafford Report 2008 update.
index-eng.php> (Version current at August 21, 2008).
<http://www.phmeg.org.uk/> (Version current at July 4, 2008).
24. Roberts RJ, Casey D, Morgan DA, Petrovic M. Comparison of 3. Harris J, Crawshaw JG, Millership S. Incidence and prevalence of wet combing with malathion for treatment of head lice in the UK: head lice in a district health authority area. Commun Dis Public A pragmatic randomized controlled trial. Lancet 2000;356:540-4.
25. Meinking TL, Clineschmidt CM, Chen C, et al. An 4. Canadian Paediatric Society, Infectious Diseases and Immunization observer-blinded study of 1% permethrin creme rinse with and Committee [Principal author: N. MacDonald]. Head lice without adjunctive combing in patients with head lice. infestations: A persistent itchy ‘pest’. Paediatr Child Health 26. Burgess IF, Brown CM, Lee PN. Treatment of head louse 5. Roberts RJ. Clinical practice. Head lice. N Engl J Med infestation with 4% dimeticone lotion: Randomized controlled 6. Jones KN, English JC III. Review of common therapeutic options 27. Kaul N, Palma KG, Silagy SS, Goodman JJ, Toole J. North in the United States for the treatment of pediculosis capitis. American efficacy and safety of a novel pediculicide rinse, isopropyl myristate 50% (Resultz). J Cutan Med Surg 2007;11:161-7.
7. Nash B. Treating head lice. BMJ 2003;326:1256-8. 28. Burgess IF, Lee PN, Brown CM. Randomised, controlled, parallel 8. Meinking TA. Infestations. Curr Probl Dermatol 1999;11:73-120. group clinical trials to evaluate the efficacy of isopropyl 9. Burkhart CN. Fomite transmission with head lice: A continuing myristate/cyclomethicone solution against head lice. Pharm J 10. Frankowski BL, Weiner LB; American Academy of Pediatrics, 29. Burgess IF, Lee PN, Matlock G. Randomised, controlled, assessor Committee on School Health, Committee on Infectious Diseases.
blind trial comparing 4% dimeticone lotion with 0.5% malathion liquid for head louse infestation. PLoS ONE 2007;2:e1127.
11. Speare R, Cahill C, Thomas G. Head lice on pillows, and strategies 30. Mumcuoglu KY, Miller J, Zamir C, Zentner G, Helbin V, Ingber A.
to make a small risk even less. Int J Dermatol 2003;42:626-9. The in vivo pediculocidal efficacy of a natural remedy. Isr Med 12. Speare R, Thomas G, Cahill C. Head lice are not found on floors in primary school classrooms. Aust N Z J Public Health 31. The National Pediculosis Association. <http://www.headlice.org/> (Version current at August 21, 2008).
Drs Robert Bortolussi, IWK Health Centre, Halifax, Nova Scotia (chair); Jane Finlay, Richmond, British Columbia; Dorothy L Moore,
The Montreal Children’s Hospital, Montreal, Quebec; Joan L Robinson, Edmonton, Alberta; Élisabeth Rousseau-Harsany, Sainte-Justine UHC,
Montreal, Quebec (board representative); Lindy M Samson, Children’s Hospital of Eastern Ontario, Ottawa, Ontario
Consultant: Dr Noni E MacDonald, IWK Health Centre, Halifax, Nova Scotia
Liaisons: Drs Upton D Allen, The Hospital for Sick Children, Toronto, Ontario (Canadian Pediatric AIDS Research Group); Charles PS Hui,
Children’s Hospital of Eastern Ontario, Ottawa, Ontario (CPS Liaison to Health Canada, Committee to Advise on Tropical Medicine and Travel);
Nicole Le Saux, Children’s Hospital of Eastern Ontario, Ottawa, Ontario (Immunization Program, ACTive); Larry Pickering, Elk Grove, Illinois,
USA (American Academy of Pediatrics); Marina I Salvadori, Children’s Hospital of Western Ontario, Ottawa, Ontario (CPS Liaison to Health
Canada, National Advisory Committee on Immunization)
Principal authors: Drs Jane Finlay, Richmond, British Columbia; Noni E MacDonald, IWK Health Centre, Halifax, Nova Scotia
The recommendations in this statement do not indicate an exclusive course of treatment or procedure to be followed. Variations, taking into account individual circumstances, may be appropriate. All Canadian Paediatric Society position statements/notes are reviewed, revised or retired as needed on a regular basis. Please consult the “Position Statements” section of the CPS website (www.cps.ca/english/publications/statementsindex.htm) for the Paediatr Child Health Vol 13 No 8 October 2008

Source: http://www.tec.srsb.ca/sites/default/files/Canadian%20Paediatric%20Society%20-%20Head%20Lice%20Policy%20Statement.pdf


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