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By popular request, the issue of food allergies will be today’s topic. I’ve been putting off posting on the subject because any submission with the word “food” (even incidentally) mentioned predisposes my personal e-mail in-box to reach “full” status prematurely and incites a plethora of unhappy comments below the post. But for you dear readers, I will bravely swim the shark infested waters of the food allergy issue.

One major point before we begin: the terms allergy and intolerance are not interchangeable. Some pets cannot tolerate certain foods. Usually, this “intolerance” manifests via some version of gastrointestinal distress (e.g., vomiting, diarrhea, gas) when the body cannot properly break down or absorb the offered foodstuff. The unwanted material then must find its way out of a GI tract unhappy to bear the load of an atypical quantity of poorly digested junk.

“Allergy” is a different story altogether. In this case, the body breaks down the food properly. Problem is, the immune system picks a fight with the would-be nutrients, mistakenly marking them as a foreign invaders. This can create problems in the GI tract (as with inflammatory bowel disorders) or, more commonly, in the faraway skin. The former typically leads to nasty cases of diarrhea or vomiting, the latter to inflammation in the skin (itchiness, hives, rashes), ear infections, hair loss, anal gland problems, hot spots, etc.

This post will deal exclusively in the far more common food allergy: the kind that keeps you up at night with the scratching of ears, the slurping of paws, or the gnawing at backs, underarms, and bellies.

Statistically speaking, dermatologic food allergies most often manifest in underarms, feet, and ears, but any spot on the skin is fair game. The lesions range from mild (as in dogs whose feet are occasionally itchy and whose ears require only a bit more attention than most) to severe. Really bad cases are way ugly; from cats with no hair and red, ulcerated patches to dogs with thick, beet red skin on their hairless legs.

(The latter I often send to the dermatologist with the satisfaction of knowing I’ve dodged a complicated bullet and secured better care for the suffering pet in one fell swoop. These severe cases are often complicated by bizarre secondary infections and require lots of patience.)

The problem is widespread among our domesticated pets. The itchiness is assumed, at first, to be no more than a flea’s bite or the inexplicable itch of the juvenile ear-scratcher. But eventually, the unrelenting discomfort renders such simple diagnoses obsolete: a trip to the vet is in order.

The vet will usually attempt to rule out parasites, hormonal imbalances, primary skin conditions, and other causes for itchiness. Sometimes antibiotics, steroids, and medicated shampoos will be prescribed to alleviate symptoms before taking the diagnostics to the next level. Once things are at a steady state and all other causes of skin irritation have been ruled out, the prospect of allergies looms large on the horizon.

It’s at this point that specific allergy testing is indicated. If the problem is relatively mild, many owners choose to fight the occasional fire of inflammation and discard the difficult and/or expensive diagnostics that allergies require.

Now remember that at this point we still have no idea what’s causing the problem (except that we have a pretty good hunch that it’s an allergy). Food, fleas, and inhalants (like pollens and grasses) are by far the most common, so these are our focus from here on out.

Fleas are a good place to start. All allergic dogs and cats in flea-prone areas should receive a high-quality topical flea medication. It matters little to me whether a flea is actually seen or not. And I don’t care how flea-free your household is. One flea a week can wreak havoc on a very sensitive pet. If after a couple of months of flea medication (and no fleas) things are no better, we then move on to the next step.

The next (and perhaps least expensive) means we employ is a “food trial,” otherwise known in derm circles as the “elimination diet” (because the goal is to eliminate all the proteins and carbohydrates the patient might have been exposed to in the past). We slowly change the pet’s diet to one of the many limited-ingredient prescription diets and wait eight weeks to see the result on the skin. Steadfast adherence to the diet (with no cheating, no treats, and no exceptions!) is a requirement.

This may seem easy to do from a outsider’s point of view, but those of us with picky or GI-sensitive pets know better. Often they won’t eat just any new diet you try. Home cooking, then, is often the end result of a properly run food trial. One additional hurdle: some owners patently refuse to undertake any diet where traditional doggie treats are not allowed. If that’s the case, or if the food trial is otherwise unsuccessful, we’re forced to move on to the next step.

Allergy testing with either blood or via pin pricks in the skin is considered more definitive than any other method. If the patient’s symptoms are severe we usually skip the flea and food trial and head straight for the good (read: expensive) stuff. Blood testing, while not so accurate, is more affordable. If you have the means, however, skin testing (undertaken by a dermatologist) is the way to go.

Let’s say you have all your results on a little piece of paper and you know exactly what foods your pet is supposed to be allergic to. Great! Now you can read tomorrow’s post for more info.

Image: Christian Mueller / Shutterstock

Last reviewed on August 5, 2015

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