Human 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. Institutions such as nursing homes, extended-care facilities, and prisons are often sites of scabies outbreaks.What is crusted (Norwegian) scabies?Crusted scabies is a severe form of scabies that can occur in some persons who are immunocompromised (have a weak immune system), elderly, disabled, or debilitated. It is also called Norwegian scabies. Persons with crusted scabies have thick crusts of skin that contain large numbers of scabies mites and eggs. Persons with crusted scabies are very contagious to other persons and can spread the infestation easily both by direct skin-to-skin contact and by contamination of items such as their clothing, bedding, and furniture. Persons with crusted scabies may not show the usually signs and symptoms of scabies such as the characteristic rash or itching (pruritus). Persons with crusted scabies should receive quick and aggressive medical treatment for their infestation to prevent outbreaks of scabies.
How soon after infestation do symptoms of scabies begin?If a person has never had scabies before, symptoms may take as long as 4-6 weeks to begin. It is important to remember that an infested person can spread scabies during this time, even if he/she does not have symptoms yet.
In a person who has had scabies before, symptoms usually appear much sooner (1-4 days) after exposure.
What are the signs and symptoms of scabies infestation?
The most common signs and symptoms of scabies are intense itching (pruritus), especially at night, and a pimple-like (papular) 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. Scratching the rash can cause skin sores; sometimes these sores become infected by bacteria.
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 (serpiginous) grayish-white or skin-colored lines on the skin surface. Because mites are often few in number (only 10-15 mites per person), these burrows may be difficult to find. They are found most often in the webbing between the fingers, in the skin folds on the wrist, elbow, or knee, and on the penis, breast, or shoulder blades.
The head, face, neck, palms, and soles often are involved in infants and very young children, but usually not adults and older children.
Persons with crusted scabies may not show the usual signs and symptoms of scabies such as the characteristic rash or itching (pruritus).
How did I get scabies?
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 is spread easily to sexual partners and household members. 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; however, such indirect spread can occur much more easily when the infested person has crusted scabies.
How is scabies infestation diagnosed?
Diagnosis of a scabies infestation usually is made based on the customary appearance and distribution of the rash and the presence of burrows. Whenever possible, the diagnosis of scabies should be confirmed by identifying the mite, mite eggs, or mite fecal matter (scybala). This can be done by carefully removing a mite from the end of its burrow using the tip of a needle or by obtaining skin scraping to examine under a microscope for mites, eggs, or mite fecal matter. It is important to remember that a person can still be infested even if mites, eggs, or fecal matter cannot be found; typically fewer than 10-15 mites can be present on the entire body of an infested person who is otherwise healthy. However, persons with crusted scabies can be infested with thousands of mites and should be considered highly contagious.
How long can scabies mites live?
On a person, scabies mites can live for as long as 1-2 months. Off a person, scabies mites usually do not survive more than 48-72 hours. Scabies mites will die if exposed to a temperature of 50°C (122°F) for 10 minutes.
Can scabies be treated?
Yes. Products used to treat scabies are 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. When treating adults and older children, scabicide cream or lotion is applied to all areas of the body from the neck down to the feet and toes; when treating infants and young children, the cream or lotion also is applied to the head and neck. The medication should be left on the body for the recommended time before it is washed off. Clean clothes should be worn after treatment.
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 reinfestation. Retreatment may be necessary if itching continues more than 2-4 weeks after treatment or if new burrows or rash continue to appear.
Never use a scabicide intended for veterinary or agricultural use to treat humans!
Who should be treated for scabies?
Anyone who is diagnosed with scabies, as well as his or her sexual partners and other contacts who have had prolonged skin-to-skin contact with the infested person, should be treated. Treatment is recommended for members of the same household as the person with scabies, particularly those persons who have had prolonged skin-to-skin contact with the infested person. All persons should be treated at the same time to prevent reinfestation.
Retreatment may be necessary if itching continues more than 2-4 weeks after treatment or if new burrows or rash continue to appear.
How soon after treatment will I feel better?
If itching continues more than 2-4 weeks after initial treatment or if new burrows or rash continue to appear (if initial treatment includes more than one application or dose, then the 2-4 time period begins after the last application or dose), retreatment with scabicide may be necessary; seek the advice of a physician.
Prevention & Control
When a person is infested with scabies mites the first time, symptoms may not appear for up to two months after being infested. However, an infested person can transmit scabies, even if they do not have symptoms. Scabies usually is passed by direct, prolonged skin-to-skin contact with an infested person. However, a person with crusted (Norwegian) scabies can spread the infestation by brief skin-to-skin contact or by exposure to bedding, clothing, or even furniture that he/she has used.
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. All household members and other potentially exposed persons should be treated at the same time as the infested person to prevent possible reexposure and reinfestation. 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.
Persons with crusted scabies and their close contacts, including household members, should be treated rapidly and aggressively to avoid outbreaks. Institutional outbreaks can be difficult to control and require a rapid, aggressive, and sustained response.
Rooms used by a patient with crusted scabies should be thoroughly cleaned and vacuumed after use. Environmental disinfestation using pesticide sprays or fogs generally is unnecessary and is discouraged.
Where Can I Get More Information?
Division of STD Prevention (DSTDP)
Centers for Disease Control and Prevention
Personal health inquiries and information about STDs:
CDC-INFO Contact Center
1-800-CDC-INFO (1-800-232-4636)
Email: cdcinfo@cdc.gov
Resources:
CDC National Prevention Information Network Web Site (NPIN)
P.O. Box 6003
Rockville, MD 20849-6003
E-mail: info@cdcnpin.org
American Sexual Health Association Web Site (ASHA)
P. O. Box 13827
Research Triangle Park, NC 27709-3827
1-800-783-9877