Mange is a severe problem caused by mites which may be passed from other infected hamsters or hay infected with mites and it is highly infectious. The hamster scratches a lot, particularly around its ears, has dry flaky skin and obvious fur loss, particularly on the back. There may also be scabs around the ears, nose and genitals.
The hamster should be isolated from any others, the cage should be thoroughly disinfected using a disinfectant specifically designed for small animal cages. Any hay should be removed and replaced with paper bedding and veterinary treatment should be sought immediately. A vet can take a skin scraping to confirm that the hamster is suffering from mange.