CANINE ALLERGIES: ART OR SCIENCE, Part 1?
Stephen Sheldon, DVM
Just like humans, dogs suffer from allergies too; in fact, researchers estimate about 1 in 5
dogs in the U.S. have some type of allergy. Colorado certainly has a higher than national
average of allergic dogs. Managing and diagnosing allergies or Atopic Dermatitis as the
disease is officially called is often difficult and frustrating. Thus many experts call it
more of an art than a science!
Atopy is an allergic skin disease with a true type one IgE mediated reaction. An allergic
reaction occurs because the immune system over reacts to a commonly occurring
substance such as pollen, grass, trees etc. The allergens are either inhaled or absorbed
through the skin; following exposure an intense de-granulation of histamine from mast
cells occurs resulting in pruritus (itching).
Atopy is widely considered a hereditary based skin disease. Some breeds predisposed to
the disorder are the terriers, dalmatians, lhasa apsos, and golden retrievers. Atopy appears
to affect male and female dogs equally. Symptoms usually begin in dogs between the
ages of 9 months to 3 years.
Allergic reactions are biologically the same in pets as in humans, but the outward
symptoms are remarkably different. People sneeze, wheeze, cough, have watery eyes, and
runny, itchy noses. Pets on the other hand have skin reactions with intense itching. Other
clues in animals are feet licking, paw chewing, face rubbing, and red, irritated ears.
Occasionally a pet will vomit or have diarrhea from an allergy (usually a food allergy).
Diagnosing allergies can be difficult. Accurate history taking is important; what some
owners consider normal activity, ie. scratching ears and licking feet, may be the first
signs of allergies. Other causes of itching need to be ruled out and can include: flea
allergies, scabies and demodectic mange, food allergies, ringworm, and skin infections
(bacterial, fungal, and yeast) to list a few. A more specific diagnosis can be obtained by
allergy testing. There are 2 methods of allergy testing, intradermal skin testing and blood
testing (either ELISA or RAST). Each has advantages and disadvantages.
For years the intradermal skin test was the standard (and only) method to check for atopy.
Skin testing is more difficult. It requires a large area of skin to be clipped, injecting 30-40
different allergens, and usually sedation (understandably!). Your pet also cannot take any
drugs for at least 2 weeks prior to testing (and up to 6 week for some drugs) which can be
quite difficult for a very itchy pet. Unfortunately, intradermal skin testing can sometimes
fail to identify some atopic dogs, and occasionally has false positive results in some dogs
without atopy.
The ELISA or RAST blood tests are quiet easy and have some advantages over
intradermal skin testing. First, they are very simple to run; your veterinarian will draw
some blood and send it to a lab. In as little as 7 days he/she will have an answer. An in-
house test available to veterinarians acts as a mini-screen for fleas, molds, pollens and
dust mites and can immediately identify highly allergic pets. Second, there is no risk or
discomfort to the patient. And thirdly, there does not appear to be any interference from
different drugs the patient may be taking. The tests are also done by different geographic
areas to help pinpoint the offending allergens. A study is currently underway to compare
the blood tests versus the skin tests in ability to identify atopic dogs.
Managing the atopic patient is really a "cookbook" approach and often requires multiple
therapies. There is no magic bullet for allergies and your veterinarian should explain all
the treatment goals. If allergens can be identified hyposensitization should be employed;
this is like making a vaccine against the allergies. Just like humans a series of injections
is given over an extended period of time (ie, biweekly, weekly, monthly etc.).
Even with hyposensitization your pet most certainly will need other modes of therapy.
What we are trying to accomplish is to raise you pet's threshold to allergens. An
important concept here is synergy. Using more than one therapeutic has a multiplied
effect rather than an added effect. Using a proper diet is important; look for the following
ingredients: fish, lamb, rice, chicken, venison, potatoes can all be helpful. Fatty acid
supplementation is also important. Antihistamines can provide relief from itching but it
can be trying to find out which ones work. I use the analogy of people and pain-relievers
here: some people get good results from aspirin, others from tylenol and still others from
motrin. It is the same with dogs and allergies and we try the following: benadryl,
chlorpheniramine, hydroxazine, and clemastine. Topical shampoos, rinses, and sprays are
also very helpful. Antibiotics are necessary if there is a concurrent skin infection. Lastly,
we have the corticosteroids (ie. prednisone, triamcinalone). You can ask 10 veterinarians
their opinions on corticosteroids and you will get 10 different answers. Used properly
they are very effective and safe; often times they are the only drug that will provide
relief! One last word about corticosteroids: they are NOT the same steroids taken by body
builders; those are anabolic steroids and are a completely different class of drugs.
As you can now see managing allergies can be difficult. It is the same in people and I'm
sure all of us know someone with allergies. Finding out what your pet is allergic to can be
of great help! We hope to control allergies; we rarely can completely cure them.
Stephen Sheldon, DVM practices at Gypsum Animal Hospital in Gypsum. Dr. Sheldon
welcomes your questions; he can be reached at 970-524-3647 or stevovet@hotmail.com.