Claim: Scabies can become crusted.

Scabies , previously known as the seven-year itch , is a contagious skin infestation by the mite Sarcoptes scabiei . The most common symptoms are severe itchiness and a pimple-like rash . Occasionally tiny burrows may be seen in the skin . When first infected , usually two to six weeks are required before symptoms occur . If a person develops a second infection later in life , symptoms may begin within a day . These symptoms can be present across most of the body or just certain areas such as the wrists , between fingers , or along the waistline . The head may be affected , but this is typically only in young children . The itch is often worse at night . Scratching may cause skin breakdown and an additional bacterial infection of the skin .   Scabies is caused by infection with the female mite Sarcoptes scabiei var . hominis . The mites burrow into the skin to live and deposit eggs . The symptoms of scabies are due to an allergic reaction to the mites . Often only between ten and fifteen mites are involved in an infection . Scabies is most often spread during a relatively long period of direct skin contact with an infected person -LRB- at least 10 minutes -RRB- such as that which may occur during sex . Spread of disease may occur even if the person has not developed symptoms yet . Crowded living conditions such as those found in child care facilities , group homes , and prisons increase the risk of spread . Areas with a lack of access to water also have higher rates of disease . Crusted scabies is a more severe form of the disease . It typically only occurs in those with a poor immune system and people may have millions of mites , making them much more contagious . In these cases spread of infection may occur during brief contact or via contaminated objects . The mite is very small and usually not directly visible . Diagnosis is based on the signs and symptoms .   A number of medications are available to treat those infected , including permethrin , crotamiton and lindane creams and ivermectin pills . Sexual contacts within the last month and people who live in the same house should also be treated at the same time . Bedding and clothing used in the last three days should be washed in hot water and dried in a hot dryer . As the mite does not live for more than three days away from human skin more washing is not needed . Symptoms may continue for two to four weeks following treatment . If after this time there continue to be symptoms retreatment may be needed .   Scabies is one of the three most common skin disorders in children , along with ringworm and bacterial skin infections . As of 2015 it affects approximately 204 million people -LRB- 2.8 % of the world population -RRB- . It is equally common in both sexes . The young and the old are more commonly affected . It also occurs more commonly in the developing world and tropical climates . The word scabies is from scabere , `` to scratch '' . Other animals do not spread human scabies . Infection in other animals is typically caused by slightly different but related mites and is known as sarcoptic mange .