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Dog Questions
Hi Dr. Berg. Our dog
is constantly biting his front paws/pads.
He causes them to bleed. We have
tried changing his diet, wrapping his paws to give them time to heal, and
Benedryl. He is an inside dog and we use
frontline for flea and tick control. I know
you have addressed this problem in your articles. Can you offer any suggestions?
DMSB, Internet
Dear DMSB,
There are many reasons a dog may bite at his front paws, but
one of the most common causes that I encounter is allergic dermatitis. Typically an allergic dog may scratch his
skin, but has an itchy face, itchy feet, and itchy ears.
There are three general types of allergy that are usually
recognized: inhalant allergy where offending materials, called allergens, are
breathed, contact allergy where allergens may come in direct contact with the
skin, and food allergy where consumption of certain material results in
allergic symptoms. The majority of all
allergies, most people believe, are due to inhalant allergy, which may also be
referred to as “Atopy.”
Inhalant allergy testing may be performed by doing skin
testing or by blood testing. Skin
testing is traditionally recognized as the “gold standard” for this type of
allergy, and is performed by injecting a series of purified extracts from materials
that are likely to cause allergic reactions in a given patient. The shaved area of skin into which the
injection is given is numbered with a marker, and the veterinarian “reads” the
numbered test sites in 10-15 minutes to see what compounds cause reactions.
Blood testing can also be used to identify inhalant
allergies, and the technique has improved to the point that, if done properly,
it can be almost as accurate as the “gold standard” injection method. When an animal becomes very itchy with allergies,
blood samples are drawn and sent to a special national laboratory that can
identify what allergies a present by examination of the blood, and a report is
faxed to the veterinarian usually within 1-2 weeks.
With either type of testing, there is usually many more than
one offending allergen demonstrated (I recently had a dog who had 24, including
“human dander”); each offending compound is graded as to how much of a reaction
occurred either in the skin or evident in the blood. Custom made serum is then prepared using
these test results, and then the owner begins a series of tiny injections to
desensitize the patient. Initially, the
injections may be given every 2-3 days, but towards the end of the procedure injections
are needed only every 3-4 weeks.
It takes patience and persistence to begin a program of
allergy injections, since it may take as long as 6-12 months before full effect
of the injections are realized. If the
testing has been done carefully and the serum correctly prepared, such a program
will work about 75% of the time. So it
is up to the owner to decide if all of this is worth it or not.
To test for a potential food allergy, an owner must feed
EXCLUSIVELY a special diet that contains items that animals are very unlikely
to react to, sometimes referred to as a “hypoallergenic diet.” These special foods usually combine an
unusual starch along with an unusual protein, so that previous exposure to the
ingredients is very unlikely. It is
believed that there must be repeated exposure to an allergen before an allergy
develops, so that dogs are very unlikely to be allergic to such diets. Some examples of hypoallergenic diets are
white fish and potato, catfish and sweet potato\ venison and potato, kangaroo
meat and potato.
To effectively run the food-testing program, you must feed
only the special diet for up to 45-60 days.
If the allergy symptoms disappear on the special diet, the owner then
adds specific ingredients one at a time to help determine which things cause
problems in the dog. Such reactions
usually happen fairly quickly, within 1-2 days.
It is important to realize that you must feed ONLY the
special diet, so that most treats and even some chew toys (rawhide chews
contain beef proteins) should not be used during this trial. Some veterinarians allow certain vegetables
to be used as a substitute treat, or may suggest freezing portions of the
hypoallergenic food in ice cube trays to make hypoallergenic “biscuits”. The entire family must help out, because it
only takes a few treats to spoil the results of the careful feeding program.
To properly diagnose and treat pet allergies takes time and
patience, but the long-term effects can be very worthwhile for you and your
dog. You may even want to ask your
veterinarian if referral to a veterinary dermatologist would be a good
idea. We are extremely fortunate to have
an excellent veterinary dermatologist close by in Newport, Dr Kevin Shanley,
who works at the Veterinary Specialty Center of Delaware as well as teaches at
the University of Pennsylvania veterinary school.
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