Vigorous scratching can break your skin and allow a secondary bacterial infection, such as impetigo, to occur. Impetigo is a superficial infection of the skin that's caused most often by staph (staphylococci) bacteria or occasionally by strep (streptococci) bacteria.
A more severe form of scabies, called crusted scabies, may affect certain high-risk groups, including:
Crusted scabies tends to be crusty and scaly, and cover large areas of the body. It's very contagious and can be hard to treat.