My cat’s ears have no fur and are very red. What is wrong?

Hair loss and redness on a cat’s ears is likely a fungal infection, or ringworm, commonly Microsporum canis. Confirm with a skin scrape, or at home use a Wood’s lamp; a green fluorescence suggests ringworm.

Once confirmed, put on an Elizabethan collar to stop scratching, disinfect with iodine and clear scales, then apply an antibacterial spray and ketoconazole ointment for fungi. Fungi spread to bedding and carpets, so clean and disinfect the environment, washing fabrics and disinfecting floors.