This is a common query. Is this a medical problem or a behavioral one? Why won't your dog stop licking, and is this harmful? These are questions without a simple answer.
Anytime there is a "behavior" involved, it is most important to first rule out an underlying medical reason for the behavior. If all medical concerns are ruled out, then the problem can be approached as a behavioral one, and behavior modification techniques can be employed.
First, though, a couple considerations: Is this a new behavior? Is it both front feet or all feet? Are there any other conditions present such as limping or swelling in the foot? A foot licking problem can start out as a medical one and later become a habit or compulsive behavior.
Although your veterinarian will be the only one able to fully determine what is going on with your dog's feet, here are some things your veterinarian will want to know and will be looking for on examination:
Are the Feet Red, Swollen, or Crusty/Flaky?
This could be indicative of a local irritant (such as deicer on the ground in the winter) or inflammation/infection from bacterial, fungal and/or parasitic sources. Even if the irritating cause is no longer present, constant licking and chewing can become a self-propagating cycle of continued trauma to the skin and continued inflammation (a condition also known as pyotraumatic dermatitis).
Could It Be Caused by Allergy, Infection or Something Else?
This could be from food allergies or atopy (inhalant allergies), causing general itchiness. Foreign bodies, such as grass awns, are also a painful and common source of infection for the feet. Arthritis or other painful internal conditions causing pain in the area without visible infection on the foot could also be a cause for licking.
Are There Any Irregular Lumps or Bumps?
Cysts or other growths or small abscesses can occur, causing discomfort and licking.
What If There Are No Signs that Something Is Wrong?
Foot licking can simply be a habit-formed behavior that occurs when the dog is relaxing, stressed, or bored. Some dogs even chew at their nails with this type of behavior.
Depending on what your veterinarian finds on examination, treatment to stop this behavior will be aimed at the underlying cause. For cases of allergy or infection, there are medications and/or dietary changes that can be made to assist with the problem.
In situations where pain is the underlying cause, that should be dealt with directly to alleviate the licking. Growths or abscesses are usually treated surgically. It is also important to be vigilant about environmental hazards to feet, such as deicing compounds in the winter and hot pavement tar in the summer. For difficult cases, a visit to a veterinary dermatologist or university veterinary teaching hospital may be in order.
Behavioral modification to stop paw licking and chewing, like any behavioral modification, takes time, patience and consistency. There are several topical products that can be used to discourage this sort of behavior.
Physical restraint, such as an e-collar, is also sometimes used for medical conditions to allow the foot or paw to heal and thus alleviate the urge to lick.
Distraction is also a good technique: playing games, offering other toys and incentives to keep your dog occupied, coupled with positive reinforcement, will help break the cycle. If additional behavior help is needed, consider working with a specialist in veterinary behavior.