Hamsters may seem to be biting themselves but they are actually scratching. This may be due to the presence of mites on the hamster's skin that cause irritation, reddening, inflammation and itchiness.
It is normal to find mites in hamsters. However, when they grow in number, they may cause skin problems characterized by rough, scaly skin and hair loss. It is difficult to see mites with the naked eye, so it is better to bring hamsters to the veterinarian for a check-up, especially when they engage in intense scratching. The vet can prescribe a topical application, including sprays, ointments or shampoos, that have mite-killing substances such as selenium sulfide or amitraz.