Scabies is caused by tiny parasitic mites. They are smaller than a pinhead and burrow into the skin and lay eggs. A more severe and uncommon form of the condition occurs when there are many mites in the skin. This is called crusted scabies, and can affect elderly and people with certain illnesses, such as AIDS.
Scabies is common. These infections are easily passed from one person to another through close body contact or sexual contact. Both men and women can get and pass them on, and it is possible for children to get scabies through close body contact.