The chewing on the paws may be from:
Flea Allergy
Flea allergy is the most common allergy in dogs and cats. It is usually not the flea bite that causes the itching, it is the flea’s saliva which causes the allergy.
Environmental or Chemical Allergens
Your dog may have been exposed to a certain chemical, pesticide, soap or seasonal pollen, which is causing his paws to be irritated. Cleaning supplies used on the floor or carpets may be too harsh on a dog’s paws. If your yard or your neighbor’s yard was recently treated with pesticides, it may be the reason his paws are bothering him. New shampoos or soaps may be causing an allergic reaction to the products. Grass pollen can cause great discomfort if your dog is allergic to it.
Food Allergies
Your dog may have itchy paws caused by a food allergy. The most common food allergens in dogs include beef, dairy, corn, wheat and soy.
Behavior Issues
Dogs sometimes bite at their paws due to stress, fear or anxiety. Boredom may be another behavior issue, which may cause the dog to chew at his paws.
Pain or Discomfort from a Foreign Object
The dog may have a spur, awn or piece of glass in his paw. Ticks sometimes burrow between the dog’s toes causing great irritation.
Corns
Corns are painful growths found on the toe pads of dogs. They are common in the Greyhound and Lurcher breeds.
Secondary Bacterial or Yeast Infection
The constant chewing, licking and biting may cause a secondary bacterial or yeast infection. The infection will cause more discomfort and itchiness.