Itchy Dogs – Is Food the Problem?
August 16, 2012
Many dog owners work hard to make their pets comfortable and
happy, so it can be frustrating when a dog is constantly itching
and distressed. Dr. Adam Patterson, clinical assistant professor
and Chief of Dermatology at the Texas A&M College of Veterinary
Medicine & Biomedical Sciences Small Animal Clinic, explained
how some perpetually itchy dogs may suffer from food allergies.
"Food allergies in dogs present themselves quite differently
than food allergies in humans," Patterson said. "For instance a
person who is allergic to shellfish may experience throat swelling
and a possibly critical or fatal reaction, but in dogs the allergy
is expressed through the skin and seen most often as itch."
Dogs who itch, lick, chew, rub, bite, and scratch themselves
year round, typically around the face, ears, armpits, groin, paws,
and around the anus may be showing signs of a food allergy. Since
itchy flare factors have an additive effect, it is important to
eliminate other possible causes of itching. First, it is necessary
to eliminate any possibility that parasites, particularly fleas,
are causing the dog to itch. Likewise, the veterinarian should also
look for signs of skin infections (bacteria and/or yeast).
Secondly, the veterinarian will also determine if environmental
factors are causing itchy skin. Dogs with year-round itch, who eat
roughly the same diet yearlong, are frequently candidates for a
food allergy diagnosis.
"There isn't a conclusive clinical skin or blood [serum] test to
see whether a dog has a food allergy," Patterson said. "It's like
flipping a coin to determine whether the test is a true or false
positive. Because of this, we have to base our diagnosis on the
dog's history, clinical signs of skin disease, and response to a
food trial. The test for food allergies in dogs simply isn't
conclusive at this time, but we hope some of our research will lead
to an effective test."
To diagnose a dog with food allergy, the first thing to do is
put the patient on an elimination diet, or an "exclusive novel
protein diet. This ends up being a diet with individual ingredients
to which the dog has rarely ever consumed before. Usually, the diet
is commercially prepared and fed for a minimum of eight weeks.
The goal is to determine if food is a component of the
Typically dogs are allergic to proteins they are exposed to for
extended periods of time. In the United States, dogs are generally
allergic to beef, chicken, and egg protein. Patterson explained
that most elimination diets replace beef, chicken, and egg based
foods with an exotic meat protein like venison, duck, kangaroo, or
vegetable-based. After eight weeks, the patient is "challenged" by
returning to the original diet. If the dog's symptoms (itch)
improved during the eight weeks, then return when the dog's
original diet is replaced, then a food allergy is confirmed.
"Patients with food allergies typically relapse within two weeks
of returning to the original diet," Patterson said. "It is
important during the elimination diet to remove any flavored
medicines or supplements, table scraps, typical treats, rawhides,
and pill pockets from the animal's diet so the test isn't
If a commercially prepared novel protein diet is not sufficient,
a prescription hydrolyzed diet may be necessary. This food is only
available by prescription from a veterinarian. It helps dogs with
food allergies by breaking down the protein into small enough
fragments that the immune system cannot recognize it, and,
therefore, does not induce a skin reaction.
Another option for dogs with food allergies is a limited
ingredient home-cooked diet. Patterson recommends only doing this
under close supervision of a veterinarian.
While any breed is susceptible to food allergies, Patterson sees
many poodles, boxers, weimaraner, dachshunds, chocolate labs, and
German shepherds with food allergies. He has also noticed dogs with
German lineages tend to be more susceptible to food allergies.
Generally dogs diagnosed with food allergies can remain on
commercially prepared elimination diets for life without
"As with any skin disease, there really isn't a cure," Patterson
said. "Instead, proper management of the disease can keep dogs
happy and healthy lifelong."
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