Food Allergies and Pets: We’re Here to Help

Treating a pet with allergies can be perplexing. It is not always possible to distinguish food allergies from flea allergies or environmental allergies (atopy). With the exception of flea allergies where flea dirt can be seen, clinical signs are usually not enough to identify the allergy involved.

Cat Eating

Like with other allergies the chief clinical sign of food allergies is red, itchy, and inflamed skin. Sometimes there is a gastrointestinal component to food allergies—often manifested as diarrhea. Whatever the cause, we are up to the challenge of getting your allergic pet feeling better.


We will work to differentiate what allergy is affecting your pet. One clue is to know the time of year an animal itches. Atopy, at least the first couple of years, tends to be seasonal. That is to say, itching is often in the springtime or late summer and fall. Environmental allergies (atopy) usually subside in the winter. However this isn’t always true as animals can become allergic to indoor allergens, too. Additionally, some animals can have both atopy and food allergies. Food may be a component year-round and atopy can push your pet over the itch threshold seasonally.

As a rule, most pets with food allergy (with no atopy) tend to have signs year-around. Because they are eating the same diet and that diet can affect the skin for weeks after ingestion. The skin will remain affected equally in July versus January as well as Monday versus Thursday. In other words it causes red, itchy skin continually without much variation.

Food Trial

The only way to diagnose food allergies definitively is with a food trial. Many legitimate allergy-testing companies that test for atopy also offer food allergy testing via blood screening. Board-certified veterinary dermatologists almost without exception agree that these blood tests are completely worthless and a waste of money. Diagnosing food allergies needs to be done with a special diet.

Food Trial Rules

  • Test for three months
    While some animals will improve within 10 to 14 days, others can take up to 3 months. Be persistent.
  • Allow only special diet and water
    One bite of the offending food can ruin the test and you will miss the diagnosis. This cannot be emphasized enough.
  • No treats.
  • Use only a veterinarian recommended diet
    For the initial trial please allow us to choose the diet.
  • Manage all your pets’ diet
    All pets in the house will need to be put on the special diet or access to other pet’s food will need to be eliminated.
  • Heartworm prevention
    Ask us if it is okay to use or if it will skew results.
  • Feed liberally
    Feed your pet slightly more food than normal. You don’t want your pet hungry and scrounging for food. If they eat something out of the garbage it may ruin the test. We’ll worry about any weight gain after diagnosis.

Non-Allergenic Diet Options

  • Most researchers believe that the processing of food makes it more allergenic. As such, probably the best food trial is a home-cooked diet. Most people don’t have access to the food needed for home-cooked diets or the time and effort to prepare them is not practical. As such, most people choose a commercial diet.

  • Typically the goal of any elimination diet is to feed 1 protein and 1 carbohydrate that is totally novel to the pet (your pet has never eaten them). In other words, we want to use a weird or obscure ingredient that your pet hasn’t been exposed to in the past. Pets can become allergic to beef, chicken, dairy, grains, or virtually any other ingredient. For our elimination diet we will choose a diet that does not have these items.

  • Another concern with choosing a diet is that while some diets appear to have limited ingredients, experience has shown they just don’t work, while other limited ingredient diets do. One theory is that manufacturing plants have traces of other foods left on equipment due to inadequate cleaning between batches of food. Again, let us help you pick the diet initially since we will recommend only foods from trusted manufacturers.

  • Another option for an elimination diet that some of our veterinarians prefer, is a hydrolyzed diet. The concept here is that even though the ingredients are common (chicken, beef etc.) the proteins, fats and carbohydrates are broken down by hydrolysis into such small particle size, the body no longer recognizes them as an allergen. This eliminates the need to determine what a pet has eaten previously and what is truly novel to that pet.

  • If we determine together that your pet is indeed food allergic, individual food items can be reintroduced to see if we can determine which ingredient is the problem. For example, if chicken is introduced and your pet reacts, we can now withdraw it and look for a commercial food without chicken. The limited antigen diets that we prescribe are certainly safe to use long-term but we sometimes switch them due to cost savings as limited antigen diets can be expensive.

    Some may ask if there isn’t a simpler way to control food allergies. Some animals will respond to steroids (cortisone), others don’t. While we are often forced to use steroids for atopy, there may be significant unwanted side effects. Therefore even if your pet’s food allergies can be controlled with steroids, it is certainly preferable to find a diet that eliminates the need for potentially dangerous drugs.

At Dupont Veterinary Clinic we care about you and your pet. We want to be your partner in making your pet comfortable and itch-free. Please don’t hesitate to call us if you have questions about your pet’s allergies.

"Thank you for taking such good care of Lola and providing a place where she feels safe. It is obvious how much you all love pets!"
— Sunshine F.