Dog Allergies Can Cause Paw Chewing

Q: I am dealing with a 5-year-old Shih Tzu that has been overbred and has a terrible problem with biting her paws. Clara has been on prednisone most of her life. I tried extremely expensive allergy tests and a year a treatment to no avail. She had been on other medications, and the prednisone is the only one that gives her some relief. I do not like the drug for her and know she needs to be off it. Paw-biting increases daily is I try to withdraw the prednisone. The rest of her coat is fine. Any information would be appreciated.

A: Paw-licking and -chewing are common signs of disease in dogs. Many owners assume these behaviors are normal and fail to recognize the extent of the problem. Genetics play a role in many cases, but overbreeding is not a specific cause. Purebred and mixed-breed dogs can chew any combination of paws, but chewing both front feet is most common. The degree of itch and obsession with the feet can vary with time of year, weather, age, diet and other factors.

The most common cause for the itch you describe is atopic dermatitis, or inhalant allergy. This is similar to hay fever in humans except that the result is usually foot-chewing rather than respiratory signs. Allergens include dust and dust mites; pollens from trees, weeds, grasses and other plants; molds; mildew; animal or human dander, including wool; and insects. Usually more than one substance is involved.

Some atopic dogs also develop skin irritation on the face, forelimbs and armpitis, among other places. Atopy also frequently causes or contributes to chronic ear and eye problems. Occasionally, dogs develop respiratory signs, such as sneezing or nasal discharge, reverse sneezing and wheezing, breathing difficulty, cough or exercise intolerance.

A dog with a flea allergy also will chew its paws. Obviously, any irritating substances can also initiate chewing, including soaps, shampoos, chemicals and foreign bodies.

Infections of the skin, hair, nails and nail beds can be the primary cause of foot-chewing and are almost always present as secondary, complicating factors in allergic situations. Infectious agents can include bacteria, yeasts, fungi and demodectic mites. Many of these organisms are normally present on the skin and only cause disease under certain conditions. Allergies can cause constant licking and subsequent swelling of the feet and accumulation of debris, creating a moist, warm environment in which overgrowth of these organisms can occur. Chewing and superficial infection allow deeper penetration of the organisms into the tissues, creating a very itchy cycle. If the suspected allergy is treated but not the secondary (or primary) infections, it is unlikely complete or lasting results will be achieved. Prednisone will relieve the itch associated with most allergies and infections, at least temporarily. Unfortunately, improper usage of prednisone andn other corticosteroids may worsen or allow infections to develop. It is important to establish a specific diagnosis and rule out complicating factors to properly address foot-chewing in dogs. Non-responsive or partially responsive cases need to be pursued further.

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