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A 42-year-old woman and her 6-year-old daughter have each been treated for head lice with two applications of over-the-counter 1% permethrin separated by 10 days. Mechanical removal of lice and their eggs was performed after each application. Environmental measures have included washing all bedding in hot water and drying at >55°C. The father’s head is shaved. Despite this, the daughter is again found to have live lice on her scalp. What measures would you recommend at this time?

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The correct answer is E. You answered E.

The answer is E. Head lice (Pediculus capitis) is a common problem among school-aged children, affecting about 1% of elementary-aged children. Nymphs and adult lice feed exclusively on human blood and need to feed at least once daily. The saliva of the lice is an irritant and produces a morbilliform rash. In some individuals, it can be urticarial. The female louse cements her eggs, called nits, firmly onto the shaft of the hair. The eggs will hatch after about 10 days. However, unless manually removed, the nit can remain attached to the hair for months afterward. Contrary to popular belief, fomite transmission of head lice is rare. Most head lice are transmitted by direct head-to-head contact. The primary symptom of an infestation is a mild pruritus. To confirm an infestation requires discovery of a live louse as finding nits only demonstrates a prior infestation but cannot confirm if it is currently active. Once confirmed, the first-line treatment is a topical application of 1% permethrin, which kills both the adult louse and the unhatched eggs. A second application should be applied after 7–10 days. However, if lice persist after this treatment, permethrin resistance may be present, and an alternative treatment should be considered. Options include lindane, malathion, benzyl alcohol, spinosad, and ivermectin. Resistance to lindane and malathion has also been reported. Lindane cannot be used in children under 110 lb. A variety of alternative treatments have been used in communities over the years including covering the scalp in mayonnaise or petrolatum jelly to suffocate the lice. These have not been demonstrated to have any efficacy. Finally, schools will determine their own policies about participation if live lice are present. However, it is unnecessary to refrain from being in school until all nits are eliminated as nits are not evidence of active infection.

 


 

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