Approach

Treatment differs according to location and local guidelines should always be consulted.

Many products and techniques exist for the treatment of head lice, but the efficacy of many has not been proved. Also, products that have previously worked well are now not uniformly effective due to the development of resistance.[30][41][42][43]

The goals of treatment are eradication of the infestation in the individual patient and minimisation of spread to others. Because there is no mortality and minimal morbidity associated with infestation, it is important that treatments are safe.[44] Choice of product or technique will depend on a number of factors, including local resistance patterns (if known), parental preference, and ease of compliance. Healthcare professionals need to be knowledgeable about each treatment method, so it can be determined if a treatment failure represents head lice resistant to the product or non-compliance in usage of the product.[45][46]

General approach to treatment

Typical first-line treatment would be a pediculicide with a neurotoxic mode of action for at least 2 treatments (preferably days 0 and 9).

For patients who prefer not to use pediculicides with a neurotoxic mode of action, products with a physical mode of action or wet combing are reasonable alternatives.[41][42][47]

Because head lice are very rarely spread via fomites, extensive hygiene practices are not necessary. More time spent on the infested child's head will yield better results.[31][32]

Pediculicides

Recommendations for the management of head lice infestation are based on the best available evidence obtained from randomised controlled trials of head-louse treatment. However, great heterogeneity in trial methodologies currently exist, such as types of treatments compared, randomisation unit, blinding, treatment-administration site, diagnosis method and criteria, and primary outcome measures. An expert panel has recommended an optimal design to standardise head-louse treatment trials, but the procedure has only been rarely followed so far.[48] Interpretation of current recommendations should take this into account.

Dimeticones are generally considered a first-line treatment but permethrin 1%, as well as pyrethrins and organophosphate compounds (with or without piperonyl butoxide), may also be recommended depending on local guidelines.[49] Dimeticones have a physical mode of action.

There is widespread resistance to permethrin 1% or pyrethrins plus piperonyl butoxide products, especially where they have been widely used over many years. Resistance patterns are complex and are usually not known for the location in which the patient lives.[50][51][52][53][54] There are also safety concerns.[55][56]

Manufacturer's directions for use need to be followed closely to ensure a safe and effective outcome. Most compounds require a second treatment after 8-10 days to ensure elimination of all parasites. In this case, parents need to be informed and reassured that seeing live lice (nymphs) after the first treatment does not necessarily indicate treatment failure or resistance and they should continue to administer the additional treatments at the recommended intervals.

In areas with known resistance to over-the-counter pediculicides, a prescription-only drug is recommended. Ivermectin topical lotion, spinosad, or malathion are suitable options. These products should only be used in patients ≥6 months of age (except malathion, which is recommended in children ≥6 years of age only).[9] Benzyl alcohol is also used in some countries, but is not available in the US. Recommendations may differ in different locations and local guidelines should be consulted.

Lindane is an organochlorine that has central nervous system toxicity in humans if used incorrectly. The US Food and Drug Administration (FDA) has issued a Public Health Advisory concerning the use of lindane, and its use has been banned in California. It has also been banned in Europe and Canada, and it is no longer recommended for the treatment of head lice.[57][58]

Essential oils and other plant-derived compounds have been widely used in traditional medicine for the eradication of head lice, but due to the variability of their constitution in commercial products, the effects may not be reproducible. Although many plants naturally produce insecticides such as pyrethrins, these agents can produce toxic effects when used by humans. The safety and efficacy of herbal products are not regulated by the FDA or other agencies, and at the present time there is insufficient evidence to recommend their use.[13][45][59][60]

Mechanical removal

There are two main methods, nit picking and wet combing, and both can be used in any age group.

Nit picking (removal of eggs and hatched egg casing) is generally not recommended as a sole technique as lice and eggs can be difficult to find and remove. It may be used to augment the efficacy of treatment with permethrin and other compounds with a neurotoxic mode of action because these have no ovicidal activity. However, repeated use of a pediculicide may kill the newly hatched nymphs without having to remove all the eggs, so it is not absolutely necessary. If undertaken, a fine-toothed lice comb can aid in removal of the nits. A fine-toothed metal comb has been shown to be best.[61] One study found that eggs can be effectively removed from the hair with the use of a commercial conditioner.[62]

Wet combing involves shampooing hair twice a week with ordinary shampoo, then vigorous combing out of wet hair with a special fine-toothed comb.[63][64][65] Success can be variable and depends largely on good technique. Combing of dry hair does not seem to have the same effect, and some have postulated that vigorous dry combing or brushing in close quarters may actually spread lice by making them airborne via static electricity.[63][66]

Battery-operated louse combs or combs with oscillating teeth may not effectively reach to the scalp and do not kill or remove nits, so offer little advantage over a well-designed traditional louse comb.[67] Battery-operated combs have not been tested in younger children, and directions state that they should not be used in anyone with a known seizure disorder. Some products claim to loosen the attachment of eggs to the hair shaft; however, vinegar-based products have not been shown to have any clinical benefit. A variety of other substances, including acetone, bleach, vodka, and mechanical releasing oils, have proved to be ineffective in loosening nits from the hair shaft and present an unacceptable risk.[68][69]

Shaving the hair on the head, while effective, is not generally a socially accepted course of action and can cause emotional trauma.

A specialist device can be used to deliver controlled heated air to desiccate lice, but currently there is insufficient evidence to advocate its widespread use.[70] A regular blow-dryer should not be used to accomplish the same result, because normal blow-dryers can cause live lice to become airborne and spread to others in the vicinity.[70] Hot air guns should never be used.

Compounds with a physical mode of action

There are several products used, and choice depends primarily on location and the age of the patient.

Dimeticones belong to the group of synthetic silicone oils. The chain length and the solvent determine the viscosity of the product and other physical properties.[71] Dimeticones with low surface tension can perfectly coat microscopic surfaces. They have a purely physical mode of action and are not neurotoxic. If applied on a louse, they coat the cuticle of the insect, enter into the spiracles (tiny tracheae-like tubes leading into the louse body), and displace the air needed for breathing. They may also disrupt water management and cause subsequent osmotic stress and probable rupture of the gut. This causes death of the parasite with a delay of several hours.[72][73] A 4% dimeticone solution in cyclomethicone showed an efficacy rate of between between 70% and 92%.[74][75][76] Another mixture of two dimeticones showed an efficacy rate of 97% in a population with a high intensity of infestation in Brazil.[77] In randomised control trials, dimeticones performed significantly better than permethrin 1% and malathion.[74][77][78] Some products also show high efficacy against eggs; however, there are no randomised controlled trials to support this.[79][80][81] Dimeticones are colorless and odorless and are considered nontoxic. Because of their mode of action, the development of resistance in lice is very unlikely. A systematic review concluded that dimeticones should be considered as the first-line treatment.[49] Dimeticones are not currently available in the US, but are used as a main treatment option in many countries in Europe, including the UK.

Petroleum jelly is thought to obstruct the respiratory spiracles of the adult louse and block holes in the operculum of the eggs. It can be used in any age group.

The Nuvo method uses Cetaphil Gentle Skin Cleanser applied to the hair and scalp, dried on with a blow-dryer, then washed out 8 hours later, with the treatment repeated once a week for 3 weeks. One study reported a 96% cure rate but the study design was inappropriate (i.e., not controlled, randomised, or blinded).[82][83] This method is only recommended in older children and adults.

Other occlusive substances have been suggested (e.g., mayonnaise, tub margarine, herbal oils, olive oil), but to date no information is available concerning efficacy.

Specific treatment strategies

Infants aged <2 months

  • Rarely occurs in this age group. Mechanical removal can be safely used. If a patient in this age group has head lice, the infestation is likely to be minimal and individual head lice can easily be seen as the hair is very thin. It is better to remove these few head lice by hand instead of putting newborns at risk of adverse effects from other treatments.

Infants aged ≥2 months and <2 years

  • Dimeticones are the first-line agent in these patients. Permethrin 1%, or pyrethrins plus piperonyl butoxide, may also be considered.

  • Ivermectin topical lotion, or spinosad are recommended in the US in areas with known resistance to first-line drugs.[9] Benzyl alcohol is also used in some countries, but is not available in the US. Recommendations for alternative options in other countries may differ and depend on availability. Local guidelines should be consulted.

  • Patients who cannot or do not want to use pediculicides with a neurotoxic mode of action, or run the risk of inducing resistance, can use mechanical removal (i.e., nit picking or wet combing).

Children aged ≥2 years and adults

  • Dimeticones are the first-line agent in these patients. Permethrin 1%, or pyrethrins plus piperonyl butoxide, may also be considered.

  • Ivermectin topical lotion, spinosad, or malathion are recommended in the US in areas with known resistance to first-line drugs.[9] Benzyl alcohol is also used in some countries, but is not available in the US. Recommendations for alternative options in other countries may differ and depend on availability. Local guidelines should be consulted.

  • Malathion is an organophosphate (cholinesterase inhibitor). Due to reports of cross-resistance with pyrethroids and safety concerns (it is highly flammable), it is considered a third-line treatment.[84][85][86][87] Although head lice resistant to malathion are common in the UK, where it has been used for decades, the preparation available in the US contains additional ingredients that themselves have a 50% cure rate, and this may delay development of resistance in the US.

  • Patients who cannot or do not want to use pediculicides with a neurotoxic mode of action, or run the risk of inducing resistance, may use mechanical removal (i.e., nit picking or wet combing).

Pregnant and lactating women

  • Most pediculicides can be used by pregnant women. However, all agents should be used with caution in lactation due to a lack of data.

  • For women who want an extra margin of safety, mechanical removal or compounds with a physical mode of action can be safely used instead.

Supportive measures

Supportive measures (e.g., cleaning hair items, bedding, or fabric items that have been in contact with an individual with an infestation) are still recommended in the US, but generally not in other countries.

Treatment of contacts

Household and other close contacts of infested individuals should be examined and treated if infested. Some experts recommend prophylactic treatment of household contacts, particularly siblings of the infested individual. Children should not be excluded or sent home early from school because of head lice. Parents of infested children (defined by visualisation of live lice) should be notified and informed that their child should be treated, ideally, before returning to school the next day. The presence of nits alone does not justify treatment.[12][3][4]

Treatment of recurrence

Treatment of recurrence depends on whether the cause is due to resistance to a particular pediculicide, incorrect initial use of a pediculicide (or other method), or re-infestation from a contact. The cause is hard to prove, and the physician may have to make an educated guess after carefully questioning the patient about the steps that were followed when using pediculicide.

If resistance to a pediculicide with a neurotoxic mode of action is likely to be the cause, an alternative treatment with a physical mode of action is recommended. If incorrect use of a pediculicide (or other method) is suspected, it is important that instructions are made clear. In this case, re-infestation can be treated as for initial infestation.

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