Hair loss on the back of a cat’s ears may mean that the cat has tinea felis. Symptoms such as hair loss, localized redness, swelling, and itching will generally occur. When this happens to a cat, the cat should be isolated first, and then taken to a pet hospital for examination and treatment. During this period, the cat should wear an Elizabethan collar to prevent the cat from licking it and getting drug poisoning, and the environment where the cat lives should be thoroughly cleaned. Disinfect to prevent bacterial growth.