SCABIES

also called Sarcoptic Itch, in human pathology, skin inflammation accompanied by severe nighttime itching caused by the cutaneous parasite Sarcoptes scabiei variety hominis, also known as the itch mite. The female mite, which attains a length of about 0.35 mm (0.014 inch), burrows beneath the superficial layer of the skin to lay two to three eggs a day within a tunnel several millimetres long. These burrows sometimes are visible as dark wavy lines. Larvae emerge from the skin after 7284 hours, moult several times, become adults in about 17 days, and mate. The initial lesion produced by the burrowing mite becomes intensely itchy after a few days to about a month, and the scratching usually leads to secondary skin lesions consisting of papules (solid elevations), pustules, and crusted skin areas. Most of the itching is believed to be caused by an allergic reaction to the chemicals produced by the mite. Scabies is most commonly noted on the webs between the fingers, other frequent locations being the natural folds of the skin and pressure areas. Transmission of the mite is by skin-to-skin contact and by contamination of clothing or bedding. The treatment of scabies is controversial. One percent lindane lotion (gamma benzene hexachloride) is standard but can be toxic. Other therapies include permethrin, a synthetic drug based on chemicals derived from the chrysanthemum.