Itching is a common problem for many people at one time or another in their lives. There are many causes of itching, from eczema to hives, from contact dermatitis to liver disease, and from medication side effects to thyroid disease. Another common cause of itching may last for years, and can even be spread from one person to another -- scabies. Scabies is caused by a skin mite which burrows in the skin, lays eggs and leaves dropping, all of which causes a very itchy skin rash. Left untreated, scabies can last for many years -- and some people even believe the term "the seven-year itch" originated from soldiers returning after World War I with scabies. Luckily, scabies is easily treated -- if the diagnosis is made as the reason for a person's itching.