According to the American Society for the Prevention of Cruelty to Animals, cats lick for a variety of reasons, including a response to stress, illness and boredom or even as a form of comfort. Cats may also suckle or lick people continuously if they have been weaned early or orphaned.
Continuous sucking and licking can lead to compulsive disorders. The ASPCA recommends that a cat who constantly licks should be checked out by a vet, especially if the cat is older. Hyperthyroidism is one illness that can cause behavior changes in cats over 10 years old. A cat should not be punished for licking. If the licking is a response to stress or anxiety, punishment may make the situation worse.