American family physician | 16 May 2019
K Gunning, B Kiraly and K Pippitt
Pediculosis and scabies are caused by ectoparasites. Pruritus is the most common presenting symptom. Head and pubic lice infestations are diagnosed with visualization of live lice. Nits (lice eggs or egg casings) alone are not sufficient to diagnose a current infestation. A “no-nit” policy for return to school is not recommended because nits can remain even after successful treatment. First-line pharmacologic treatment for pediculosis is permethrin 1% lotion or shampoo. Newer treatments are available but costly, and resistance patterns are generally unknown. Noninsecticidal agents, including dimethicone and isopropyl myristate, show promise in the treatment of pediculosis. Extensive environmental decontamination is not necessary after pediculosis is diagnosed. In adults, the presence of pubic lice should prompt an evaluation for sexually transmitted infections. Body lice infestation should be suspected in patients with pruritus who live in crowded conditions or have poor hygiene. Scabies in adults presents as a pruritic, papular rash in a typical distribution pattern. In infants, the rash can also be vesicular, pustular, or nodular. First-line treatment for scabies is permethrin 5% cream. Clothing and bedding of persons with scabies should be washed in hot water and dried in a hot dryer. Counseling regarding appropriate diagnosis and correct use of effective therapies is key to reducing the burden of lice and scabies.
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