Although a person can acquire crab lice from bedding, clothing or toilet seats, the primary means of infestation is direct sexual contact, during which the louse moves from one host to another. Persons engaging in oral sex can be infected in the hair of the eyelashes, eyebrows, face, chest or scalp. An infected parent can pass lice on to children through close contact. Symptoms Infected persons often discover the lice accidentally or learn about them from an infected partner. Otherwise, itching in the pubic area is a telltale sign.
Adult lice appear as small, silver-amber flecks, the nits as shiny ovals cemented to the hair.
Distinctive sky-blue spots mark the parasite's bites and defecation. These will fade to brownish specks. The usual means of diagnosis is a report of infestation by the victim or clinical observation of the symptoms. This is left on for 12 hours. Infestations of the scalp are treated with a 10-minute lindane shampoo, followed by a thorough rinse.