Scabies (/ˈskeɪbiːz, ˈskeɪbiiːz/;[10] also sometimes known as the seven-year itch)[1] is a contagious human skin infestation by the tiny (0.2–0.45 mm) mite Sarcoptes scabiei,[1][3] variety hominis.

[2] Scabies most often spreads during a relatively long period of direct skin contact with an infected person (at least 10 minutes) such as that which may occur during sexual activity or living together.

[13] Crowded living conditions, such as those found in child-care facilities, group homes, and prisons, increase the risk of spread.

[14] Several medications are available to treat those infected, including oral and topical ivermectin, permethrin, crotamiton, and lindane creams.

[19] The superficial burrows of scabies usually occur in the area of the finger webs, feet, ventral wrists, elbows, back, buttocks, and external genitals.

[21] In most people, the trails of the burrowing mites are linear or S-shaped tracks in the skin, often accompanied by rows of small, pimple-like mosquito or insect bites.

Lesions are symmetrical and mainly affect the hands, wrists, axillae, thighs, buttocks, waist, soles of the feet, areola, and vulva in females, and penis and scrotum in males.

[citation needed] In the 18th century, Italian biologists Giovanni Cosimo Bonomo and Diacinto Cestoni (1637–1718) described the mite now called Sarcoptes scabiei, variety hominis, as the cause of scabies.

Gravid females tunnel into the dead, outermost layer (stratum corneum) of a host's skin and deposit eggs in the shallow burrows.

In general, the total number of adult mites infesting a healthy hygienic person with non-crusted scabies is small, about 11 females in burrows, on average.

[26] The movement of mites within and on the skin produces an intense itch, which has the characteristics of a delayed cell-mediated inflammatory response to allergens.

IgE antibodies are present in the serum and the site of infection, which react to multiple protein allergens in the body of the mite.

Less commonly, scabies infestation can happen through the sharing of clothes, towels, and bedding, but this is not a major mode of transmission; individual mites can survive for only two to three days, at most, away from human skin at room temperature.

[28][29] As with lice, a latex condom is ineffective against scabies transmission during intercourse, because mites typically migrate from one individual to the next at sites other than the sex organs.

The allergic reaction is both of the delayed (cell-mediated) and immediate (antibody-mediated) type, and involves IgE (antibodies are presumed to mediate the very rapid symptoms on reinfection).

[15] To detect the burrow, the suspected area is rubbed with ink from a fountain pen or a topical tetracycline solution, which glows under a special light.

[33] Mass-treatment programs that use topical permethrin or oral ivermectin have been effective in reducing the prevalence of scabies in several populations.

The simultaneous treatment of all close contacts is recommended, even if they show no symptoms of infection (asymptomatic), to reduce rates of recurrence.

[15] Since mites can survive for only two to three days without a host, other objects in the environment pose little risk of transmission except in the case of crusted scabies.

[15] In addition to treating the infestation, options to control itchiness include antihistamines and prescription anti-inflammatory agents.

[50] A study has demonstrated that scabies is markedly reduced in populations taking ivermectin regularly;[51] the drug is widely used for treating scabies and other parasitic diseases, particularly among the poor and disadvantaged in the tropics, beginning with the developer Merck providing the drug at no cost to treat onchocerciasis from 1987.

Large-scale mass drug administration strategies may be required where coordinated interventions aim to treat whole communities in one concerted effort.

Furthermore, since endemic scabies is largely restricted to poor and remote areas, it is a public health issue that has not attracted much attention from policymakers and international donors.

[58] Globally as of 2009, an estimated 300 million cases of scabies occur each year, although various parties claim the figure is either over- or underestimated.

[20][60] In the fourth century BC, Aristotle reported on "lice" that "escape from little pimples if they are pricked" – a description consistent with scabies.

[62] Roman encyclopedist and medical writer Aulus Cornelius Celsus (circa 25 BC – 50 AD) is credited with naming the disease "scabies" and describing its characteristic features.

[61] The parasitic etiology of scabies was documented by Italian physician Giovanni Cosimo Bonomo (1663–1696) in his 1687 letter, "Observations concerning the fleshworms of the human body".

The contents and origins of several versions of the ointment were detailed in correspondence published in the British Medical Journal in 1945.

[63] In the 1995 documentary Anne Frank Remembered, Bloeme Evers-Emden told of how she was selected from Auschwitz and sent to a work camp where conditions were sufficiently improved that she was able to survive until the liberation.

[69][70][71][72] The International Alliance for the Control of Scabies was started in 2012,[6][57][73] and brings together over 150 researchers, clinicians, and public-health experts from more than 15 countries.