Pet Food Allergies: What Are Food Elimination Diets?

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This post was original published on the Petfinder Blog

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Dr. V is a veterinarian and the author of Pawcurious, a blog that tackles humorous, educational, and touching topics. Each day Dr. V wrestles with dogs, cats, and emotions in the drama of life in a small-animal vet clinic. Today she shares her experiences with pet food allergies and explains what an elimination diet is.

Two years ago, my then-7-year-old cat Apollo strolled by, plopped on the floor, and revealed that he had big patches of fur missing on his thighs. Since he was an all-black cat to begin with, it was pretty obvious, and pretty ugly.

It took me six months to figure out what was wrong with my mangy scoundrel. Between the blood tests, biopsies, skin scrapes, and even the course of Prozac, he continued to lick and remove ever increasing patches of fur. Running out of options, I considered the possibility of a food allergy, and changed him to a novel-protein prescription diet. Eight weeks later, Apollo got his groove (and his fur) back.

Allergies are a challenge to diagnose, and of the three main kinds — fleas, food, and the environment — food is the toughest. The signs are variable: Some pets show no signs other than chronic ear infections. Others itch so badly we think they have scabies, while still others lick their paws non-stop. The signs are very similar to those seen in other disease processes, and there is no one definitive sign that screams, “Change my food!”

There is only one way to diagnose a food allergy, and that is by putting your pet on an elimination diet. There is no blood test, no skin test, no other way to do it. In short, you put the pet on a hypoallergenic diet and see if they get better.

It sounds deceptively simple. I have people tell me all the time, “Oh, Rover doesn’t have food allergies. I changed him from a chicken food to a lamb-and-rice formula and he’s still itchy.” That is NOT a hypoallergenic diet! If you read the labels on a bag of food, you might be amazed to see just how many lamb formulas have chicken as their primary protein source!

There are only two types of commercial diets appropriate for a food trial: hydrolyzed soy diets and novel-ingredient diets. In both cases, the diets contain a single protein source and a single carbohydrate source. The novel-protein diets are called such because the protein source is something unlikely to be in any other commercial diet: Examples are duck, venison, and even kangaroo. The carbohydrate is also something unusual: often potatoes or peas.

Hydrolyzed soy diets (mmm, doesn’t that sound tasty?) involve taking the protein and breaking it down so small the body doesn’t recognize it as an antigen. Both types of diets are readily available from veterinarians. Home cooking is also a possibility, but you should get guidance from your veterinarian as to the best way to do so if that is something you are interested in.

Here’s the kicker: It takes eight to 12 weeks to see results. Eight to 12 weeks of a very restricted diet: no scraps, no unapproved treats, no nibbles of the other pet’s kibble.

Once your pet’s allergies are under control, you have two options:

  1. Stay on the special diet (a lot of the companies are making corresponding treats to make this easier for pets).
  2. Do a “challenge.” Every week, pick one thing: chicken, corn, wheat, beef, etc. For two to three days feed your pet some of that one ingredient. See what happens.

Once you determine the offender(s), you can look for an over-the-counter diet that does not contain that ingredient. Manufacturers have become increasingly savvy to this need and there are lots of really good options out there with limited allergens.

It is a challenge, to be sure. But as the owner of an allergic pet myself, I can vouch for the dramatic results: It’s worth the effort!

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