Scabies is caused by an infestation of the skin by the human itch mite (Sarcoptes scabiei var. hominis). The microscopic scabies mite burrows into the upper layer of the skin where it lives and lays its eggs. The most common symptoms of scabies are intense itching and a pimple-like skin rash. The scabies mite usually is spread by direct, prolonged, skin-to-skin contact with a person who has scabies.
Scabies occurs worldwide and affects people of all races and social classes. Scabies can spread rapidly under crowded conditions where close body contact is frequent.
Signs and Symptoms of Scabies
When a person is infested with scabies mites the first time, symptoms usually do not appear for up to two months (2-6 weeks) after being infested. If a person has had scabies before, symptoms appear much sooner (1-4 days) after exposure.
The most common signs and symptoms of scabies are intense itching, especially at night, and a pimple-like itchy rash. The itching and rash each may affect much of the body or be limited to common sites such as the wrist, elbow, armpit, webbing between the fingers, nipple, penis, waist, belt-line, and buttocks. The rash also can include tiny blisters (vesicles) and scales.
Tiny burrows sometimes are seen on the skin; these are caused by the female scabies mite tunneling just beneath the surface of the skin. These burrows appear as tiny raised and crooked grayish-white or skin-colored lines on the skin surface. The mites are often few in number (only 10-15 mites per person), so these burrows may be difficult to find.
Complications of Scabies
The intense itching of scabies leads to scratching that can lead to skin sores. The sores sometimes become infected with bacteria on the skin, such as Staphylococcus aureus. Sometimes the bacterial skin infection can lead to an inflammation of the kidneys called post-streptococcal glomerulonephritis.
How Scabies Spreads
Scabies usually is spread by direct, prolonged, skin-to-skin contact with a person who has scabies. Contact generally must be prolonged; a quick handshake or hug usually will not spread scabies. Scabies in adults frequently is sexually acquired. Scabies sometimes is spread indirectly by sharing articles such as clothing, towels, or bedding used by an infested person.
A person infested with scabies mites can transmit scabies, even if they do not have symptoms, until they are successfully treated and the mites and eggs are destroyed.
How Scabies is Treated
Treatment for scabies involves either oral medications or topical creams called scabicides because they kill scabies mites; some also kill eggs. Scabicides to treat human scabies are available only with a doctor’s prescription; no “over-the-counter” (non-prescription) products have been tested and approved for humans. Always follow carefully the instructions provided by the doctor and pharmacist, as well as those contained in the box or printed on the label.
In addition to the infested person, treatment also is recommended for household members and sexual contacts, particularly those who have had prolonged skin-to-skin contact with the infested person. All persons should be treated at the same time in order to prevent re-infestation. Retreatment may be necessary if itching continues more than 2-4 weeks after treatment or if new burrows or rash continue to appear.
In addition to medicinal treatment, bedding and clothing should be decontaminated (i.e., either machine-washed, machine-dried using the hot cycle, or dry cleaned) or removed from body contact for at least 72 hours. Fumigation of living areas is not necessary.
How to Prevent Scabies
Scabies is prevented by avoiding direct skin-to-skin contact with an infested person or with items such as clothing or bedding used by an infested person. Scabies treatment usually is recommended for members of the same household, particularly for those who have had prolonged skin-to-skin contact. Bedding and clothing worn or used next to the skin anytime during the 3 days before treatment should be machine washed and dried using the hot water and hot dryer cycles or be dry-cleaned. Items that cannot be dry-cleaned or laundered can be disinfested by storing in a closed plastic bag for several days to a week. Scabies mites generally do not survive more than 2 to 3 days away from human skin. Children and adults usually can return to child care, school, or work the day after treatment.
Source: Centers for Disease Control and Prevention - www.cdc.gov/scabies