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1Insect Research & Development Limited, Cambridge, UK
IB has been a consultant to various makers of pharmaceutical products, alternative therapies, and combs for treating louse infestations. He is also co-author of one RCT referenced in this review.
Head lice can only be diagnosed by finding live lice, as eggs take 7 days to hatch and may appear viable for weeks after death of the egg. Infestation may be more likely in school children, with risks increased in children with more siblings, longer hair, and of lower socioeconomic group.
Methods and outcomes
We conducted a systematic review and aimed to answer the following clinical question: What are the effects of treatments for head lice? We searched: Medline, Embase, The Cochrane Library, and other important databases up to June 2008 (Clinical Evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).
Results
We found 15 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.
Conclusions
In this systematic review we present information relating to the effectiveness and safety of the following interventions: dimeticone, herbal and essential oils, insecticide combinations, lindane, malathion, mechanical removal by combing (‘bug busting’), oral trimethoprim-sulfamethoxazone (co-trimoxazole, TMP-SMX), permethrin, phenothrin, and pyrethrum.
Key Points
Head lice can only be diagnosed by finding live lice, as eggs take 7 days to hatch, and may appear viable for weeks after death of the egg.
Infestation may be more likely in school children, with risks increased in children with more siblings, longer hair, or of lower socioeconomic group.
Malathion lotion may increase lice eradication compared with phenothrin or permethrin. Current best practice is to treat with two applications 7 days apart, and to check for cure at 14 days.
Studies comparingmalathion or permethrin with wet combing have given conflicting results, possibly due to varying insecticide resistance.
Permethrin may be more effective at eradicating lice compared with lindane.
Head lice are obligate ectoparasites of socially active humans. They infest the scalp and attach their eggs to the hair shafts. Itching, resulting from multiple bites, is not diagnostic, but may increase the index of suspicion. Eggs glued to hairs, whether hatched (nits) or unhatched, are not proof of active infection, because eggs may retain a viable appearance for weeks after death. A conclusive diagnosis can only be made by finding live lice. One observational study compared two groups of children with louse eggs but no lice at initial assessment. Over 14 days, more children with five or more eggs within 6 mm of the scalp developed infestations compared with those with fewer than five eggs. Adequate follow-up examinations using detection combing are more likely to be productive than nit removal to prevent reinfestation. Infestations are not self-limiting.
Incidence/
Prevalence
We found no studies on incidence and few recently published studies of prevalence in resource-rich countries. Anecdotal reports suggest that prevalence has increased in the past few years in most communities in Europe, the Americas, and Australasia. A recent cross-sectional study from Belgium (6169 children, aged 2.5-12.0 years) found a prevalence of 8.9%. An earlier pilot study (677 children, aged 3-11 years) showed that in individual schools the prevalence was as high as 19.5%. One cross-sectional study from Belgium found that head lice were significantly more common in children from families with lower socioeconomic status (OR 1.25, 95% CI 1.04 to 1.47), in children with more siblings (OR 1.2, 95% CI 1.1 to 1.3), and in children with longer hair (OR 1.20, 95% CI 1.02 to 1.43), although hair length may influence the ability to detect infestation. The socioeconomic status of the family was also a significant influence on the ability to treat infestations successfully — the lower the socioeconomic status, the greater the risk of treatment failure (OR 1.70, 95% CI 1.05 to 2.70).
Aetiology/
Risk factors
Observational studies indicate that infestations occur most frequently in school children, although there is no evidence of a link with school attendance.
We found no evidence that lice prefer clean hair to dirty hair.
Prognosis
The infestation is almost harmless. Sensitisation reactions to louse saliva and faeces may result in localised irritation and erythema. Secondary infection of scratches may occur. Lice have been identified as primary mechanical vectors of scalp pyoderma caused by streptococci and staphylococci usually found on the skin.
Aims of
intervention
To eliminate infestation by killing or removing all head lice and their eggs.
Outcomes
Treatment success is given as the percentage of people completely cleared of head lice. There are no standard criteria for judging treatment success or what constitutes infestation. Trials used different methods, and in many cases the method was not reported. Few studies were pragmatic.
Methods
Clinical Evidence search and appraisal June 2008. The following databases were used to identify studies for this review: Medline 1966 to June 2008, Embase 1980 to June 2008, and The Cochrane Library (all databases) 2008, Issue 2. Additional searches were carried out using these websites: NHS Centre for Reviews and Dissemination (CRD) (all databases), Turning Research into Practice (TRIP), and NICE. Abstracts of the studies retrieved from the initial search were assessed by an information specialist. Selected studies were then sent to the author for additional assessment, using predetermined criteria to identify relevant studies. Study design criteria for evaluation in this review were: published systematic reviews and RCTs in any language, at least single blinded (if possible), and containing 20 or more individuals of whom more than 80% were followed up. There was no minimum length of follow-up required to include studies. In addition, we use a regular surveillance protocol to capture harms alerts from organisations such as the FDA and the UK Medicines and Healthcare products Regulatory Agency (MHRA), which are added to the review as required. The initial search was performed by the Cochrane Infectious Diseases Group at the Liverpool School of Tropical Medicine for a systematic review compiled in July 1998 (now withdrawn). Established infestations with head lice do not resolve spontaneously. Consequently, placebo-controlled studies are considered unethical and are no longer reported here. We have performed a GRADE evaluation of the quality of evidence for interventions included in this review (see table
). To aid readability of the numerical data in our reviews, we round many percentages to the nearest whole number. Readers should be aware of this when relating percentages to summary statistics such as RRs and ORs.
Table.
GRADE evaluation of interventions for head lice
Important outcomes
Clearance of infestation, adverse effects
Number of studies (participants)
Outcome
Comparison
Type of evidence
Quality
Consistency
Directness
Effect size
GRADE
Comment
What are the effects of treatments for head lice?
1 (193)
Eradication rate
Malathion v phenothrin
4
–1
0
–1
0
Low
Quality point deducted for sparse data. Directness point deducted for uncertainty about interventions
1 (66)
Eradication rate
Malathion v permethrin
4
–1
–1
-1
0
Very Low
Quality point deducted for sparse data. Consistency point deducted for different results at different end points. Directness point deducted for differences of intervention
2 (205)
Eradication rate
Malathion v mechanical removal ("bug busting")
4
–1
–1
–1
0
Very low
Quality point deducted for sparse data. Consistency point deducted for conflicting results. Directness point deducted for second RCT including different interventions and non-standard dose.
1(73)
Eradication rate
Malathion v dimeticone
4
–1
0
–1
0
Low
Quality point deducted for sparse data. Directness point deducted for uncertain generalisability
7 (726)
Eradication rate
Permethrin v lindane
4
0
0
0
0
High
1 (133)
Eradication rate
Permethrin v mechanical removal ("bug busting")
4
–1
0
–1
0
Low
Quality point deducted for sparse data. Directness point deducted for inclusion of other intervention and non-standard doses
1 (115)
Eradication rate
TMP-SMX v permethrin
4
–2
0
–1
0
Very low
Quality points deducted for sparse data and poor quality of follow-up. Directness point deducted for inclusion of other intervention, non-identical comparators, and non-standard doses
1 (115)
Eradication rate
TMP-SMX plus permethrin v permethrin alone
4
–2
0
–1
0
Very low
Quality points deducted for sparse data and poor quality of follow-up. Directness point deducted for inclusion of other intervention, non-identical comparators, and non-standard doses
1 (143)
Eradication rate
Combined insecticides v herbal oils
4
–2
0
–1
0
Very low
Quality points deducted for sparse data and failure to explain high withdrawal rate. Directness point deducted for uncertain generalisability of herbal product outcome
1 (253)
Eradication rate
Dimeticone v phenothrin
4
0
0
–1
0
Moderate
Directness point deducted for uncertain generalisability of intervention
1 (73)
Eradication rate
Dimeticone v malathion
4
–1
0
–1
0
Low
Quality point deducted for sparse data. Directness point deducted for uncertain generalisability
1 (30)
Eradication rate
Mechanical removal ("bug busting") v phenothrin
4
–2
0
–1
0
Very low
Quality points deducted for sparse data and different follow-up for different groups. Directness point deducted for uncertain generalisability of intervention
1 (95)
Eradication rate
Permethrin plus combing v permethrin alone
4
–1
0
–1
0
Low
Quality point deducted for sparse data. Directness point deducted for uncertain generalisability
Type of evidence: 4 = RCT; 2 = Observational; 1 = Non-analytical/expert opinion. Consistency: similarity of results across studies. Directness: generalisability of population or outcomes.Effect size: based on relative risk or odds ratio.
Glossary
High-quality evidence
Further research is very unlikely to change our confidence in the estimate of effect.
Low-quality evidence
Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.
Moderate-quality evidence
Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.
Pediculicide
Any compound or material (possibly a pesticide) that kills lice. This term is used specifically in place of “insecticide” as not all pediculicides are recognised pesticides. A pediculicide is distinct from an “ovicide”, which kills louse eggs, although one substance may fulfil both functions.
Pragmatic RCT
An RCT designed to provide results that are directly applicable to normal practice (compared with explanatory trials that are intended to clarify efficacy under ideal conditions). Pragmatic RCTs recruit a population that is representative of those who are normally treated, allow normal compliance with instructions (by avoiding incentives and by using oral instructions with advice to follow manufacturers' instructions), and analyse results by “intention to treat” rather than by “on treatment” methods.
Scalp pyoderma
Scalp pyoderma involves impetigo-like bacterial infections that result from scratching. In most cases they are caused by streptococci, with some staphylococcal involvement. Scalp pyoderma of this type is closely associated with long term louse infestation.
Very low-quality evidence
Any estimate of effect is very uncertain.
Disclaimer
The information contained in this publication is intended for medical professionals. Categories presented in Clinical Evidence indicate a judgement about the strength of the evidence available to our contributors prior to publication and the relevant importance of benefit and harms. We rely on our contributors to confirm the accuracy of the information presented and to adhere to describe accepted practices. Readers should be aware that professionals in the field may have different opinions. Because of this and regular advances in medical research we strongly recommend that readers' independently verify specified treatments and drugs including manufacturers' guidance. Also, the categories do not indicate whether a particular treatment is generally appropriate or whether it is suitable for a particular individual. Ultimately it is the readers' responsibility to make their own professional judgements, so to appropriately advise and treat their patients.To the fullest extent permitted by law, BMJ Publishing Group Limited and its editors are not responsible for any losses, injury or damage caused to any person or property (including under contract, by negligence, products liability or otherwise) whether they be direct or indirect, special, incidental or consequential, resulting from the application of the information in this publication.
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ERADICATION RATE Compared with phenothrin: Malathion lotion may be more effective at increasing lice eradication rates ( low-quality evidence ). Compared with permethrin: Malathion may be more effective at eradicating head lice at 14 days, but not at 7 days (very low-quality evidence). Compared with mechanical removal ('bug busting'): The effects of malathion compared with wet combing with conditioner (“bug busting”) are unclear ( very low-quality evidence ). Compared with dimeticone: Malathion may be less effective at increasing eradication of head lice at 14 days (low-quality evidence) NOTE We found no clinically important results about the effects of malathion compared with herbal treatments, pyrethrum, lindane, or trimethoprim–sulfamethoxazone (TMP-SMX, co-trimoxazole).
Benefits
Malathion versus phenothrin:
We found no systematic review but found one RCT. The RCT (193 school children) compared 0.5% malathion alcoholic lotion (applied for 8 hours or overnight) versus 0.3% d-phenothrin lotion, and found that malathion increased lice eradication rates after 1 day compared with phenothrin (louse free: 87/95 [92%] with malathion v 39/98 [40%] with phenothrin; RR 2.3, 95% CI 1.7 to 2.9). This difference had increased by day 7 (90/95 [95%] with malathion v 38/98 [39%] with phenothrin; RR 2.4, 95% CI 1.8 to 3.2; see comment below).
Malathion versus permethrin:
We found no systematic review but we found one RCT. The RCT compared 0.5% alcoholic malathion lotion (applied for 20 minutes) versus 1% permethrin cream rinse (applied for 10 minutes). Both products were applied once, with a second application after 7 days if lice were found. The RCT found no significant difference between treatments in the proportion of people free of lice after 7 days (66 children and adults; AR for being lice free: 33/41 [80.5%] with malathion v 13/22 [59.1%] with permethrin; P = 0.08). However, it found that malathion significantly increased the proportion of people free of lice after 14 days (40/41 [97.68%] with malathion v 12/22 [54.5%] with permethrin, P less than 0.0001).
Malathion versus pyrethrum or lindane:
We found no systematic review and no RCTs comparing malathion with pyrethrum or lindane.
Malathion versus mechanical removal of lice:
We found no systematic review but one RCT (72 schoolchildren) compared “bug busting” (wet combing with conditioner) versus two applications of 0.5% malathion (27 alcoholic lotion, 13 aqueous liquid each applied for 8 hours or overnight) 7 days apart (see comment below). It found that malathion significantly improved lice eradication rates after 14 days compared with “bug busting” (lice free: 31/40 [78%] with malathion v 12/32 [38%] with “bug busting”; RR 2.07, 95% CI 1.30 to 3.30).
Malathion or permethrin versus mechanical removal of lice:
We found one RCT comparing “bug busting” (wet combing with conditioner) versus a single application of pediculicide (0.5% aqueous malathion applied 8 hours or overnight or 1% permethrin cream rinse applied for 10 minutes; see comment below). Treatment success was measured at 5 days for the pediculicide group and at 15 days for the “bug busting” group. The RCT found that pediculicide was less effective than “bug busting” at increasing the proportion of people free of lice at follow-up (133 children and adolescents, aged 2–15 years; lice free: 9/70 [13%] with pediculicide v 32/62 [52%] with bug busting; see comment below).
Malathion versus herbal treatments:
We found no systematic review and no RCTs comparing malathion with herbal treatments.
Malathion versus trimethoprim–sulfamethoxazole (TMP-SMX, co-trimoxazole):
We found no systematic review and no RCTs comparing malathion versus TMP-SMX.
Malathion versus dimeticone:
We found no systematic review but one RCT comparing malathion versus dimeticone. The RCT (73 children and adults) compared two applications of 0.5% aqueous malathion (applied 8 hours or overnight) 7 days apart versus two applications of 4% dimeticone lotion (applied 8 hours or overnight) 7 days apart (see comment below). The RCT assessed “cure” defined as no evidence of either head lice after the second treatment, or of reinfestation after cure. It found that malathion was significantly less effective than 4% dimeticone after 14 days (AR for treatment success: 10/30 [33%] with malathion v 30/43 [70%] with dimeticone, difference –36%, 95% CI –60% to –13%, P less than 0.01).
Harms
Malathion versus permethrin:
The RCT reported no adverse effects associated with permethrin. One person (1/41 [2%]) complained of scalp burning with malathion and the product was washed off early. Stinging was likely to be as a result of the vehicle used (alcohol with terpenoid).
Malathion versus pyrethrum or lindane:
We found no RCTs.
Malathion versus mechanical removal of lice:
The RCT (72 people) found that one participant complained of stinging on application of malathion, and the product was washed off early. Stinging was likely to be as a result of the vehicle used (alcohol with terpenoid).
Malathion or permethrin versus mechanical removal of lice:
The RCT gave no information on adverse effects.
Malathion versus herbal treatments:
We found no RCTs.
Malathion versus TMP-SMX:
We found no RCTs.
Malathion versus dimeticone:
The RCT reported no adverse effects associated with dimeticone. Two people (2/30 [7%]) reported itching or irritation of the neck or scalp during treatment with malathion.
Comment
The RCT comparing malathion versus phenothrin found that some children who were not free from lice on day 1 had become louse free by day 7 in both groups, suggesting that some parental intervention had influenced the results. The RCT also concluded that about 60% of treatments may have been affected by pyrethroid insecticide resistance. In vitro testing confirmed some lice as being tolerant of phenothrin. The other RCT looking at “bug busting” was designed to be a pragmatic RCT with results applicable to normal practice. Studies in vitro suggest that other components of the products (e.g. terpenoids and solvents) may be more effective pediculicides than the insecticide itself. This is supported by the relatively high level of cure achieved using the formulation vehicle in some “placebo”-controlled trials. Resistance to one or more insecticides is now common.
The RCT comparing “bug busting” versus malathion or permethrin used a single application of each product, which is not current best practice (see Clinical guide); in addition, the insecticide-treated group was only followed for 5 days, which is inadequate to confirm efficacy, as the eggs take 7 days to hatch. In the pediculicide group, 30 people (43%) received malathion and 40 people (57%) received permethrin. Most people in the pediculicide group who did not have successful eradication were found to have pyrethroid-resistant lice.
Clinical guide:
Current best practice is to treat with two applications 7 days apart to ensure treatment of louse nymphs emerging from eggs not killed by the first treatment. Most investigators agree that a final examination after 14 days is necessary to determine cure.
Substantive changes
Malathion One RCT added comparing malathion versus dimeticone. It found that malathion was less effective than dimeticone at eradicating headlice at 14 days. Categorisation unchanged (Likely to be beneficial)
ERADICATION RATE Compared with malathion: Permethrin may be less effective at eradicating head lice at 14 days, but not at 7 days ( low-quality evidence ). Compared with lindane: Permethrin is more effective at increasing eradication rates ( high-quality evidence ). Compared with mechanical removal ('bug busting'): Permethrin may be less effective at eradicating lice in a population with a high prevalence of insecticide resistance (low-quality evidence). Compared with trimethoprim–sulfamethoxazone (TMP-SMX, co-trimoxazole): Permethrin may be as effective as TMP-SMX when used as monotherapy to eradicate head lice ( very low-quality evidence ). Compared with TMP-SMX plus permethrin: Permethrin alone may be less effective at eradicating head lice (very low-quality evidence). NOTE We found no clinically important results about the effects of permethrin compared with phenothrin, pyrethrum, dimeticone, or herbal treatments.
Benefits
Permethrin versus phenothrin or pyrethrum:
We found no systematic review or RCTs comparing permethrin with these insecticides.
Permethrin versus malathion:
See benefits of malathion.
Permethrin versus lindane:
We found one systematic review (7 RCTs, 726 people, search date 1995). The systematic review found that permethrin (1% cream rinse) significantly increased eradication rates compared with lindane (1% shampoo) after 14 days (2 RCTs; OR for not clearing head lice 15.2, 95% CI 8.0 to 28.8).
Permethrin versus mechanical removal of lice:
We found no systematic review or RCTs of permethrin compared with mechanical removal of lice alone.
Permethrin or malathion versus mechanical removal of lice:
See benefits of malathion.
Permethrin versus herbal treatments:
We found no systematic review or RCTs.
Permethrin versus trimethoprim–sulfamethoxazole (TMP-SMX, co-trimoxazole):
See benefits of oral TMP-SMX.
Permethrin versus dimeticone:
We found no systematic review or RCTs.
Combing plus insecticide versus insecticide alone:
See benefits of mechanical removal of lice or viable eggs by combing.
Harms
The reviews reported no adverse effects following treatment with permethrin.
Permethrin or malathion versus mechanical removal of lice:
See harms of malathion.
Permethrin versus trimethoprim–sulfamethoxazole (TMP-SMX, co-trimoxazole):
See harms of TMP-SMX.
Combing plus insecticide versus insecticide alone:
See harms of mechanical removal of lice or viable eggs by combing.
Permethrin versus phenothrin or pyrethrum:
We found no RCTs.
Permethrin versus mechanical removal of lice:
We found no RCTs of permethrin compared with mechanical removal of lice alone.
ERADICATION RATE Compared with permethrin: Trimethoprim–sulfamethoxazone (TMP-SMX, co-trimoxazole) may be as effective as permethrin when used as monotherapy to eradicate head lice ( very low-quality evidence ). TMP-SMX plus permethrin compared with permethrin alone: Combined treatment with TMP-SMX plus permethrin may be more effective at increasing eradication (very low-quality evidence). ADVERSE EFFECTS TMP-SMX is associated with intense pruritus after 3–4 days, and with potentially rare but serious adverse effects, including Stevens–Johnson syndrome, erythema multiforme, and blood disorders. NOTE We found no clinically important results about the effect of TMP-SMX compared with malathion, phenothrin, pyrethrum, lindane, mechanical removal of lice, dimeticone, or herbal treatments.
Benefits
Trimethoprim–sulfamethoxazole (TMP-SMX, co-trimoxazole) (oral) versus permethrin or combination treatment:
We found one RCT comparing three treatments: oral TMP-SMX alone (10 mg/kg/day over 10 days); 1% topical permethrin alone (1 application with a second 1 week later if required); and 1% topical permethrin plus oral TMP-SMX. The RCT defined treatment success as the absence of adult lice, nymphal stages, or eggs. However, the investigators did not evaluate all outcomes. The RCT found no significant difference at 4 weeks between TMP-SMX alone, permethrin alone, and the combination treatment (115 children, aged 2–13 years; AR for treatment success: 28/36 [78%] with TMP-SMX alone v 28/39 [72%] with permethrin alone v 37/40 [93%] with combination treatment; TMP-SMX v permethrin, P = 0.74; TMP-SMX v combination treatment, P = 0.14). However, it found that the combined treatment significantly increased the proportion of people with treatment success at 4 weeks compared with permethrin alone (P = 0.03).
TMP-SMX (oral) versus malathion, phenothrin, pyrethrum, lindane, mechanical removal of lice, dimeticone, or herbal treatments:
We found no systematic review or RCTs.
Harms
Trimethoprim–sulfamethoxazole (TMP-SMX, co-trimoxazole) (oral) versus permethrin or combination treatment:
The RCT (115 children) found that five children taking TMP-SMX reported nausea/vomiting, minor rash, or both, and that three children reported scalp irritation with permethrin. It found that 9/36 (25%) children developed intense pruritus after 3–4 days with TMP-SMX alone, but the pruritus disappeared after 1–3 hours and treatment was continued. Three children were withdrawn due to rash caused by TMP-SMX. Rare but serious potential adverse effects of TMP-SMX include Stevens–Johnson syndrome, erythema multiforme, and blood disorders. The RCT did not find any cases of these severe adverse effects with TMP-SMX.
Comment
Clinical guide:
Given the potential harms arising from the use of TMP-SMX, the relatively high incidence of other adverse effects, and the marginal benefit compared with conventional treatment, it is unlikely that TMP-SMX would present as a treatment of choice for head lice infestation. This might primarily be viewed as a therapeutic curiosity, especially as alternative treatment not involving potentially toxic agents (e.g. with materials like dimeticone) is likely to become standard practice in the next few years.
ERADICATION RATE Compared with herbal treatments: A combination of insecticides (permethrin plus malathion, synergised with piperonyl butoxide) may be as effective as a herbal product (coconut, anise, and ylang ylang) at eradicating head lice ( very low-quality evidence ). NOTE We found no RCTs comparing combinations of insecticides versus single agents, trimethoprim–sulfamethoxazole (TMP-SMX, co-trimoxazole), or mechanical removal of lice.
Benefits
Combinations of insecticides versus mechanical removal of lice:
See benefits of mechanical removal of lice or viable eggs by combing.
Combinations of insecticides versus herbal treatment:
See benefits of herbal treatments.
Combination of insecticides versus single agents:
We found no systematic review or RCTs comparing combinations of insecticides with single non-herbal agents.
Combination of insecticides versus trimethoprim–sulfamethoxazole (TMP-SMX, co-trimoxazole):
We found no systematic review or RCTs.
Harms
Combinations of insecticides versus herbal treatment:
The RCT found no clinically detectable adverse effects with either a spray made from herbal oils (a mixture of coconut, anise, and ylang ylang) or insecticide spray (permethrin plus malathion, synergised with piperonyl butoxide). A potential for toxic effects has been recognised for several essential oils.
ERADICATION RATE Compared with phenothrin: Dimeticone 4% lotion and 0.5% phenothrin liquid seem equally effective at eradicating lice ( moderate-quality evidence ). Compared with malathion: Dimeticone may be more effective at eradicating head lice at 14 days ( low-quality evidence ). NOTE We found no clinically important results about the effects of dimeticone compared with herbal and essential oils, lindane, permethrin, mechanical removal, pyrethrum, or oral trimethoprim–sulfamethoxazole (TMP-SMX, co-trimoxazole).
Benefits
Dimeticone versus phenothrin:
We found one RCT comparing 0.5% phenothrin aqueous liquid versus 4% dimeticone in a volatile silicone vehicle (both groups used 2 applications 7 days apart). The RCT assessed “cure” defined as no evidence of head lice after the second treatment, or of reinfestation after cure. It found no significant difference between dimeticone and phenothrin in the proportion of people cured (214 young people and 39 adults; AR for cure: 89/127 [70%] with dimeticone v 94/125 [75%] with phenothrin; difference: –5%, 95% CI –16% to +6%).
Dimeticone versus malathion:
See benefits of malathion.
Dimeticone versus herbal and essential oils, lindane, permethrin, mechanical removal, pyrethrum, or oral trimethoprim–sulfamethoxazole (TMP-SMX, co-trimoxazole):
We found no systematic reviews or RCTs comparing dimeticone versus these treatments.
Harms
Dimeticone versus phenothrin:
The RCT found significantly fewer irritant scalp reactions with dimeticone compared with phenothrin (3/127 [2%] with dimeticone v 11/125 [9%] with phenothrin; difference: 6%, 95% CI 1% to 12%).
Dimeticone versus malathion:
See harms of malathion.
Dimeticone versus malathion, herbal and essential oils, lindane, permethrin, mechanical removal, pyrethrum, or oral trimethoprim–sulfamethoxazole (TMP-SMX, co-trimoxazole):
We found no RCTs.
Comment
Clinical guide:
Dimeticone does not act on the insect nervous system and is unlikely to be affected by resistance to other insecticides. These RCTs were conducted in an area where resistance to insecticides is widespread.
Therefore the results may not be generalisable to other dimeticone formulations and application times. See comment on phenothrin.
Substantive changes
Dimeticone One RCT added comparing dimeticone versus malathion. It found that dimeticone was more effective than malathion at eradicating headlice at 14 days. Categorisation changed from Unknown effectiveness to Likely to be beneficial.
ERADICATION RATE Compared with combined insecticide: A herbal product (coconut, anise, and ylang ylang) may be as effective as a combination of insecticides (permethrin plus malathion, synergised with piperonyl butoxide) at eradicating head lice ( very low-quality evidence ). NOTE We found no clinically important results about the effects of herbal products compared with malathion, permethrin, phenothrin, pyrethrum, lindane, dimeticone, or trimethoprim–sulfamethoxazole (TMP-SMX, co-trimoxazole).
Benefits
Herbal and essential oils versus malathion, permethrin, phenothrin, pyrethrum, lindane, dimeticone, or trimethoprim–sulfamethoxazole (TMP-SMX, co-trimoxazole):
We found no systematic review or RCTs comparing herbal treatments with these treatments.
Herbal and essential oils versus combinations of insecticides:
We found no systematic review. We found one RCT (143 children) comparing a spray based on herbal oils (coconut, anise, and ylang ylang; concentrations unspecified) versus an insecticide spray (0.5% permethrin plus 0.25% malathion, synergised with 2% piperonyl butoxide). The herbal spray was used three times at 5-day intervals and the insecticide twice with 10 days between applications. The RCT found no significant difference in eradication rates between the herbal product and the insecticide (60/70 [86%] with herbal product v 59/73 [81%] with insecticide).
Harms
Herbal and essential oils versus combinations of insecticides:
The RCT found no clinically detectable adverse effects with either herbal oils (a mixture of coconut, anise, and ylang ylang) or insecticide spray (permethrin plus malathion, synergised with piperonyl butoxide). A potential for toxic effects has been recognised for several essential oils.
Comment
Results may not generalise to different concentrations of these herbal ingredients or to other herbal products. The study may not be generalisable as the herbal treatment regimen was non-standard and the withdrawal rate high.
Clinical guide:
Sprays are not a good vehicle for delivery of pediculicides owing to the risks of inhalation and of spraying into the eyes.
ERADICATION RATE Compared with permethrin: Lindane is less effective at eradicating head lice ( high-quality evidence ). ADVERSE EFFECTS The possibility of central nervous system toxicity from lindane has led to its withdrawal in some countries. NOTE: We found no clinically important results about the effects of lindane compared with other insecticides, mechanical removal of lice, herbal treatments, or trimethoprim–sulfamethoxazole (TMP-SMX, co-trimoxazole).
Benefits
Lindane versus malathion, phenothrin, pyrethrum, mechanical removal of lice, herbal treatments, dimeticone, or trimethoprim–sulfamethoxazole (TMP-SMX, co-trimoxazole):
We found no systematic review or RCTs that compared lindane with these treatments.
Lindane versus permethrin:
See benefits of permethrin.
Harms
There are extensive reports of central nervous system effects related to overdosing (treatment of scabies) and absorption (treatment of head lice) with lindane. Transdermal passage of lindane occurs during treatment of head lice, but we found no reports of adverse effects in this setting.
Comment
See comment on malathion.
Substantive changes
No new evidence
BMJ Clin Evid. 2009 Jan 14;2009:1703.
Mechanical removal of lice or viable eggs by combing
ERADICATION RATE Compared with malathion: We don't know how effective wet combing with conditioner (“bug busting”) is ( very low-quality evidence ). Compared with pediculicide treatment (malathion or permethrin): "Bug busting" (using a plastic comb) may be more effective at eradicating lice in a population with a high prevalence of insecticide resistance ( low-quality evidence ). Compared with phenothrin plus combing: Mechanical removal ("bug busting") using a plastic comb and conditioner may be more effective at eradicating lice (very low-quality evidence). Combing plus permethrin compared with permethrin alone: Permethrin plus adjuvant combing (using a metal comb) and permethrin alone may be similarly effective at eradicating lice (low-quality evidence). NOTE We found no clinically important results about the effects of mechanical removal compared with pyrethrum, dimeticone, or lindane.
Benefits
Combing versus malathion:
See benefits of malathion.
Combing versus permethrin:
We found no systematic review or RCTs comparing combing alone versus permethrin.
Combing versus malathion or permethrin:
See benefits of malathion.
Combing versus phenothrin:
See benefits of phenothrin.
Combing versus pyrethrum:
We found no systematic review or RCTs.
Combing versus lindane:
We found no systematic review or RCTs.
Combing plus insecticide versus insecticide alone:
We found one RCT (95 adults and children) comparing combing with a metal louse/nit comb plus 1% permethrin cream rinse versus permethrin cream rinse alone. In both groups, permethrin was applied by a community practitioner, and if lice were found after 7 days there was a further application of permethrin, or permethrin plus combing. The RCT found no significant difference in eradication rates with adjuvant combing compared with permethrin alone at 2, 8, and 15 days (louse free rates, at day 2: 49/59 [83%] with no combing v 24/33 [73%] with combing; RR 1.14, 95% CI 0.90 to 1.50; at day 8 before repeat treatment: 27/59 [46%] with no combing v 11/33 [33%] with combing; RR 0.92, 95% CI 0.60 to 1.40; at day 15: 47/60 [78%] with no combing v 24/33 [73%] with combing; RR 1.08, 95% CI 0.80 to 1.40).
Combing plus combination insecticides:
We found two RCTs comparing different pediculicides in combination with nit combing, but none included a non-combing or non-insecticide control group.
Combing versus dimeticone:
We found no systematic review or RCTs.
Harms
Apart from discomfort, we found no evidence of harms from combing. Wet combing with conditioner may cause adverse reactions, which have been observed during normal cosmetic use.
Comment
Combing versus malathion:
The RCT comparing “bug busting” versus malathion was designed as a pragmatic RCT with results applicable to normal practice.
Combing versus phenothrin:
See comment on phenothrin. It is possible that some of the effect attributed to the combing element of “bug busting” may actually be because of the activity of conditioners on head lice and their eggs. A non-RCT has indicated that a conditioner-like formulation was an effective pediculicide if allowed to dry on the hair. A similar effect could occur if combing during “bug busting” takes long enough.
ERADICATION RATE Compared with malathion: Phenothrin may be less effective at eradicating head lice ( low-quality evidence ). Compared with dimeticone: 0.5% phenothrin liquid and 4% dimeticone lotion seem similarly effective at eradicating lice ( moderate-quality evidence ). Compared with mechanical removal: Phenothrin plus combing may be less effective at eradicating head lice ( very low-quality evidence ). NOTE: We found no clinically important results about the effects of phenothrin compared with permethrin, pyrethrum, or lindane.
Benefits
Phenothrin versus malathion:
See benefits of malathion.
Phenothrin versus permethrin, pyrethrum, or lindane:
We found no systematic review and no RCTs comparing phenothrin versus these insecticides.
Phenothrin versus mechanical removal of lice:
We found no systematic review but we found one RCT (30 people) comparing “bug busting” versus phenothrin alcoholic lotion (two applications 7 days apart, concentration not reported) plus combing. It found that phenothrin lotion plus combing was significantly less effective at eradicating head lice after 14 days compared with “bug busting” (eradication rates: 2/15 [13%] with phenothrin v 8/15 [53%] with “bug busting”; RR 0.25, 95% CI 0.06 to 1.00). However, results were confounded by other differences between treatment groups (see comment below).
Phenothrin versus herbal treatments:
We found no systematic review or RCTs comparing phenothrin versus herbal treatment.
Phenothrin versus dimeticone:
See benefits of dimeticone.
Phenothrin versus trimethoprim–sulfamethoxazole (TMP-SMX, co-trimoxazole):
We found no systematic review or RCTs.
Harms
Phenothrin versus mechanical removal of lice:
The RCT reported that there were no harms throughout the study period.
Phenothrin versus dimeticone:
See harms of dimeticone.
Comment
See comment on malathion.
Phenothrin versus mechanical removal of lice:
In the RCT comparing “bug busting” with phenothrin lotion, the interventions were applied by trained nurses. “Bug busting” involved the use of different graded combs and specific hair conditioner, whereas people in the phenothrin group used a single head-lice comb and unspecified hair conditioners. The follow-up strategy for the combing group differed from that offered to the lotion group. This difference may introduce bias and confounding. The RCT was conducted in an area where resistance to pyrethroid insecticides was widespread. The results of this RCT may not be generalisable to other product formulations and application times.
Clinical guide:
Phenothrin lotion is applied for only 2 hours compared with 12 hours or overnight for the liquid formulation. The liquid formulation contains solvents that may contribute towards the activity. Therefore, if a phenothrin product is to be used, the liquid formulation may be more likely to be effective.
We found no clinically important results about the effecets of pyrethrum compared with other insecticides, mechanical removal of lice, herbal treatments, or trimethoprim–sulfamethoxazole (TMP-SMX, co-trimoxazole).
Benefits
Pyrethrum versus other insecticides, mechanical removal of lice, herbal treatments, dimeticone, or trimethoprim–sulfamethoxazole (TMP-SMX, co-trimoxazole):
We found no systematic review or RCTs comparing pyrethrum versus these treatments.
Harms
There are no reports of harms related to the use of pyrethrum.
