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Human scabies is caused by an infestation of the skin by the human itch mite (Sarcoptes scabiei var. hominis). This microscopic mite burrows into the upper layer of the skin where it lives and lays eggs. Scabies is typically spread by prolonged, direct, skin-to-skin contact with an infested individual. The most common signs and symptoms are intense itching and a pimple-like skin rash. The more severe form of scabies referred to as crusted, or Norwegian, scabies could occur in elderly, disabled, debilitated, or individuals with decreased immune systems. Patients with crusted scabies develop thick crusts of skin that contain a large number of mites and eggs. Scabies and crusted scabies can be prevented by avoiding direct, skin-to-skin and indirect contact with infested individuals.
Scabies is common throughout the world and affects people of all races and social classes. The female mite that causes scabies burrows into the upper layer of the skin where it lives and deposits eggs. The mite is passed from human-to-human by direct, prolonged, skin-to-skin contact with a person who is infested. Therefore, this condition can spread easily in crowded conditions such as nursing homes, child care facilities, extended-care facilities, and prisons. In adults, it is frequently sexually acquired.
The more severe form of scabies referred to as crusted, or Norwegian, scabies involves a greater number of mites infesting the affected individual (up to 2 million per patient). Thus, this form of scabies is much more contagious and may involve spreading not only via direct skin-to-skin contact but also indirect. Patients with this severe form may shed the mite and contaminate items such as clothing, bedding, and furniture. Immunocompromised, elderly, disabled, or debilitated individuals may be at higher risk for developing crusted, or Norwegian, scabies.
What are the signs and symptoms of scabies?
The most common signs and symptoms of scabies are intense itching and a pimple-like (popular) itchy rash. If the rash is scratched, this may result in sores that could become infected with bacteria. This itching sensation and rash may affect most of the body or may be limited to specific sites, such as the wrist, elbow, waist, armpit, penis, nipple, buttocks, between the fingers, or the belt-line.
In addition, tiny burrows from the tunneling of the female scabies mites may occasionally be observed. These tunnels are often tiny raised and crooked gray-white lines on the skin surface. However, since only a few mites (10-15 mites/person) are typically present, the tunnels may not be observed.
An infested person can spread scabies even without demonstrating any symptoms. This is because the first time a person becomes infested, they may not illustrate any signs or symptoms for the first 2 to 6 weeks.
Individuals infested with crusted, or Norwegian, scabies may not demonstrate the characteristic rash or itching. Patients have thick crusts of skin that contain a large number of mites and eggs.
How is scabies diagnosed?
Scabies diagnosis is typically made based on the presence of burrows and the characteristic appearance and distribution of the rash. Ideally the diagnosis should be confirmed by identifying the mite, which can be accomplished by carefully removing the mite from the end of a burrow using a needle tip or by skin scraping. Given that scabies patients may only be infested with 10-15 mites, the mites, eggs, or fecal matter may be difficult to observe.
How can scabies be treated?
Products that are used to treat scabies are referred to as scabicides as they kill scabies mites. If you believe that you have scabies, please seek medical attention from your health care provider. Scabicides are only available with a doctor's prescription. These products are typically in the form of a lotion. If skin sores become infected, antibiotics may also be warranted.
Patients with crusted scabies and all of their close contacts should be treated rapidly and aggressively in attempts to prevent an outbreak.
Treatment is recommended for both sexual and close personal contacts who have had prolonged skin-to-skin contact with an infested individual within the preceding month. Everyone should receive treatment at the same time in order to help prevent re-infestation. Bedding, clothing, and towels that were used by an infested individual or by anyone within that household anytime during the three days before treatment should be washed in hot water and dried in a hot dryer, or needs to be dry-cleaned, or sealed in a plastic bag for a minimum of 72 hours. The use of insecticide sprays or fumigants is not recommended.
Additional information regarding treatment can be found following the links below.
How can I prevent scabies?
Scabies is spread by direct, prolonged, skin-to-skin contact with an infested individual. This condition is typically spread easily to sexual partners and/or household members. It may be acquired indirectly after using a towel, clothing, or bedding that an infested patient utilized prior. However, this indirect spread is more common with the crusted, or Norwegian, form of scabies.
Scabies can be prevented by avoiding direct skin-to-skin contact with an infested individual or with personal items, such as bedding and clothing that was used by the infested individual. Bedding, clothing, and towels that were used by an infested person or by other household members anytime during the three days before treatment, should be washed in hot water and dried in a hot dryer, or needs to be dry-cleaned, or sealed in a plastic bag for a minimum of 72 hours. Typically the scabies mites do not survive for more than 2 to 3 days away from human skin. The rooms that patients with crusted scabies stayed in should be thoroughly cleaned and vacuumed after use. Fumigation is not recommended.
Humans are the source of human scabies; animals do not spread the human form of this condition. Pets can become infested with a different form of the mite, resulting in “mange.” The animal mite cannot survive on human skin, however, it could cause temporary irritation. The animal however, should be treated by a veterinarian.