Doctor's Notes on Scabies
Sacbies is a contagious skin disease caused by an infestation of the skin by a mite known as Sarcoptes scabiei. It is transmitted from person to person by direct skin contact with an infested person. Sexual contact is also a common means of transmission.
Signs and symptoms of scabies include itching that can become very severe, especially at night. There is an associated rash that appears to resemble pimples. The rash of scabies is most commonly seen around the wrists, armpits, elbows, between the fingers and toes, around the nails, and in areas of skin skin usually covered by clothing including the buttocks, belt line, nipples, and penis. Another associated symptom is the presence of "burrows," which are thin gray, brown, or red lines on the skin that lead away from the bumps.
Symptoms occur from two to six weeks to appear after exposure. They include severe and continuous itching, especially at night.
- The skin may show signs of small insect-type bites, or the lesions may look like pimples, bumps, or blisters, especially around the wrist, elbow, knee, underarm area, groin, or finger webs. The skin may also have redness, rash, or have sores (welts, bumps or nodules, especially in children, termed nodular scabies) due to scratching of the area. Large nodules of 2-20 mm in diameter may appear in infants unable to scratch.
- A burrow (a short S-shaped track that indicates the mite's movement under the skin) may also be visible, especially in the webs of fingers and toes. Burrows may be small enough to be overlooked. Thus, scabies also should be considered whenever there is intense itching and/or scratching, even without an obvious rash, bite, or burrow. Ulcers are not frequently formed.
- Scabies frequently occur in the crevasses of the body such as between the fingers and toes, the buttocks, the elbows, the waist area, the genital area, and under the breasts in women. The face, neck, head, scalp, palms, soles of the feet, and lips are usually not affected, except in infants or very young children.
- Risk factors such as immune suppression or old age may predispose patients to more extensive disease. In crusted (Norwegian) scabies, the body of the infested person is covered with a thick, dry, and scaly rash. The rash of crusted scabies may or may not itch, but it contains thousands to millions of mites. Crusted scabies is the most contagious form of scabies and the hardest to treat.
- Many other skin rashes may look like scabies, including allergic drug reactions, contact dermatitis, and viral rashes such as shingles.
Scabies is caused by an eight-legged mite (Sarcoptes scabiei var. hominis) that is less than 0.5 mm long. Worldwide, about 300 million people are infected each year. In the U.S., there were outbreaks of scabies in 10 schools in Texas and in hospital workers in Charlotte, N.C., in 2015.
Scabies is a skin condition caused by an infestation of the human itch mite called Sarcoptes scabiei. These microscopic mites burrow into the skin and cause symptoms of itching and rash.
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Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.