Scabies

I

Introduction

Scabies, skin disease caused by a tiny parasite called an itch mite. Scabies causes severe itching and is highly contagious. Itch mites are usually spread by close skin-to-skin contact with an infected person; holding hands is sufficient. As a result scabies spreads easily and rapidly in crowded conditions or where there is a lot of close contact with others, especially in daycare centers and nursing homes. Sexual contact is another means of transmission.

II

How Scabies Develops

Scabies occurs when the female mite burrows into the outer layers of the skin, where she deposits eggs and wastes. These deposits irritate the skin and cause an allergic reaction that manifests itself in severe itching and, in many cases, a rash or small bumps on the skin. The mites can infest any part of the body, but they most often burrow into folds of the skin—between the fingers; on the elbow, wrist, or knees; around the shoulder blades; on the buttocks or the penis; or under the breasts in women. The itching and rash generally begin about a month after the infestation. Itching may become more intense at night or after a hot bath. Scratching the itchy skin can lead to sores through which bacteria may enter and cause infection.

The itch mite that most commonly causes scabies is the female of the species Sarcoptes scabiei. This pearly white, microscopic member of the arachnid family, to which spiders also belong, measures less than 0.05 cm (0.02 in) long.

III

Diagnosis and Treatment of Scabies

A dermatologist (skin doctor) can usually diagnose scabies by sight. The physician may confirm the diagnosis by scraping a portion of the skin and examining the scrapings under a microscope for the presence of mites or eggs. The treatment for scabies consists of applying a lotion that kills the mites, larvae, and eggs. Several lotions are available, but a lotion containing permethrin is most often prescribed. The lotion must be applied all over the body, not just on the affected area. The physician may also prescribe an antihistamine to control the itching.

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The mites that cause scabies can live for a few days in bedding or clothing. To prevent others in the household from developing the condition, it is important to wash in hot water any sheets, towels, or clothes that have come into contact with the infected person. Scabies can recur. Someone treated for scabies has been sensitized by the mite and will react much more quickly if exposed again to the mite.

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