Scabies is a contagious skin infestation by the mite Sarcoptes scabiei. The most common symptoms are severe itchiness and a pimple-like rash. The elderly disabled and people with an impaired immune system like those with HIV, cancer or those on immunosuppressive medications are susceptible to crusted scabies. On those with weaker immune systems the host becomes a more fertile breeding ground for the mites which spread over the host's body except the face. The mites in crusted scabies are not more virulent than in noncrusted scabies; however, they are much more numerous. People with crusted scabies exhibit scaly rashes, slight itching and thick crusts of skin that contain large numbers of scabies mites. For this reason persons with crusted scabies are more contagious to others than those with typical scabies. Such areas make eradication of mites particularly difficult as the crusts protect the mites from topical scabicides necessitating prolonged treatment of these areas.