Human scabies is caused by the human itch mite (Sarcoptesscabiei, variation or subtype hominis). This itch mite burrows into the upper layers of skin and lays its eggs in the skin. This itch mite is found worldwide and often causes outbreaks in places where people are living close together, such as dormitories, nursing homes, institutions, or prisons. The rash often includes areas such as the web spaces of the fingers, wrists, beltline, feet, scrotum, and areolas, but other areas may get infected.
Is scabies contagious?
Scabies is contagious. However, it usually requires fairly long skin-to-skin contact with an infested person (for example, carrying a person, sleeping with the person, or sexual partners). Infrequently, it may be contagious through contact with clothing or bedding, but this form of transfer of scabies is thought to be very infrequent. In general, most people who become infested with scabies usually have about 10-15 itch mites on their body. One exception to this rule is a scabies infestation that is seen less frequently called crusted or Norwegian scabies, in which large areas of skin are infected with huge numbers (thousands) of itch mites; a person with this type of scabies is highly contagious. Although pets can become infested with similar itch mites, they are not usually spread from humans to animals or from animals to humans.
How will I know if I have scabies? What is the incubation period for scabies?
People usually know if they have scabies from the presence of a very itchy rash that has little tendrils that extend out of an area of itchy rash (these are the burrows that the itch mite makes in the skin layers), especially if they have noticed similar skin changes on a person with whom they may have had close contact. Some physicians may do skin scrapings and, with fairly common laboratory stains, may identify the mite and/or its eggs or fecal matter in the skin scrapings viewed with a microscope. In young children, pinkish-brown nodules may form on the skin. The incubation period for scabies can be up to eight weeks; the infested person can be contagious during this period.
How is scabies transmitted?
Scabies is spread by direct and usually prolonged skin-to-skin contact with a person who has the disease. Indirect spread can sometimes occur through contaminated clothing or towels. Crusted or Norwegian scabies is highly contagious, both from direct contact and indirect contact (from clothing, bedding, towels, for example) because of the very high concentration of mites.
How will I know if I am cured of scabies?
Scabicides like permethrin are used topically (spread onto skin) to kill the itch mites. Usually, a cream or lotion is applied from the neck down to the feet, and the cure results in remission and finally disappearance of the rash. However, sometimes people may seem to be cured only to have itching and the rash return in a few weeks. This may be due to inadequate treatment that allows the eggs to survive and hatch or may be due to inadequate cleaning of clothing or bedding (scabies mites are killed by hot water and dryer heat, or dry cleaning, and cannot survive more than two or three days away from human skin) or simply due to contacting someone who has scabies. If there is no further symptom development about two to four weeks after treatment, most people will be cured of scabies.
If you or someone close to you has scabies, contact a physician for treatment and for advice about who else may benefit from treatment (for example, sexual partners, family members). Patients with crusted scabies require isolation and/or barriers (gloves, gowns, for example) to protect others from the mites; such patients often are hospitalized and also tested for underlying health problems (such as immunosuppression).