Inflammation around the teeth, periodontal disease and other mouth diseases can cause an obvious smell. Cats are good at hiding pain and may keep going to the food bowl even though chewing hurts. Drooling, dropping food, chewing on one side or choosing softer food can therefore be important clues.
Looking in the mouth of an awake cat shows only part of the problem. To assess gum pockets, tooth roots and changes below the gum line, an examination under anaesthesia and dental X-rays are often needed. Tooth brushing can reduce new plaque but cannot repair tissue already destroyed by advanced periodontal disease.
Book a dental assessment for persistent bad breath, red gums, drooling or changed eating behaviour. If your cat stops eating or has obvious swelling of the face, it should be examined urgently.