Food Allergies in Dogs and Cats


A food allergy is a reaction to food which triggers a response from the body’s immune system. In dogs and cat, proteins are usually the offending substances responsible for adverse food reactions. For this reason, feeding the grain-free/gluten free and boutique diets which are recent fads, is not only unnecessary and expensive, but potentially harmful. (See July 2018New Studies Debunk Today’s Myths about Pet Food.) The immune reaction to food may be manifested by itching and/or gastrointestinal signs, such as chronic vomiting, diarrhea, frequent bowel movements, and gas. Sometimes chronic ear infections are the only sign of food allergy.

Allergies vs. Adverse Food Reactions and Food Intolerance

There are differing opinions among dermatologists concerning how common true food allergies are. Part of this may be due to the fact that in the clinical setting, true food allergies are usually not distinguished from adverse food reactions and food intolerance, which do not trigger an immune response. However, true food allergies are probably much less common than environmental allergies. Still, frustrated pet owners, in an attempt to relieve a pet’s itching, often try a plethora of new foods, hoping to find something that will work, and frequently end up disappointed.

Is Your Dog Prone to Food Allergies?

Certain breeds tend to be more susceptible to food allergies, including:

So God created the great sea creatures and every living creature that moves, with which the waters swarm, according to their kinds, and every winged bird according to its kind. And God saw that it was good. Genesis 1:21

  • Labrador Retrievers
  • Cocker Spaniels
  • German Shepherds
  • West Highland White Terriers
  • Bichon Frise, Collies
  • Cairn Terriers
  • Irish and English Setters
  • Golden Retrievers
  • Dalmations
  • Shar Pei
  • Lhasa apso
  • Miniature Schnauzers
  • Siamese and Birman cats

This list is not exclusive, as other breeds, as well as mixed breeds can also be afflicted with food allergies.

Is it actually a Food Allergy?

Some clues to help rule determine if a food allergy is likely include:

  1. The age at which the symptoms occur. Up to half of food allergic animals exhibit symptoms at less than one year of age.
  2. The symptoms are year-round. However, keep in mind that animals with food allergies may also have environmental and/or flea allergies, so there may be some increased itching during certain times of the year.
  3. Steroids, which are very effective in relieving the itching associated with other allergies, may not work as well for food allergies.
  4. Gastrointestinal signs are present in approximately 1/3 of food allergic patients.
  5. Although food allergic dogs may exhibit itching anywhere on the body, feet licking, and ear infections, one of the common signs of food allergy is a “flaming anus,” which is redness around the anal region and under the tail. Cats often have itching around the face and neck, hair loss, and scabs.

Testing for Food Allergies

Unfortunately, there is no diagnostic blood or skin test for food allergy. Although some labs offer testing for food allergies, these are not reliable. A positive antibody test to a certain protein can simply mean the pet has eaten that protein, not that it is allergic to it.

A definitive diagnosis requires a therapeutic (prescription) food trial in which a novel protein (protein the animal has never eaten), hydrolyzed (low antigen therapeutic diet), or homemade (only with the help of a certified veterinary nutritionist) is fed for at least eight weeks. Sometimes it is necessary to continue for 10-12 weeks.

Commercial diets sold over the counter (OTC) may claim to be hypoallergenic or good for sensitive skin, however these claims have no official meaning. Immunological tests on OTC foods found that many of them contain additional proteins or contaminants, which is legal as they are not produced for food trials. While it is tempting to try OTC foods as a cheaper alternative to therapeutic diets, feeding these foods can defeat the purpose of the food trial. Therapeutic diets are made by pet food companies to specifically contain the same ingredients without contamination. In addition, if your pet will not eat the diet, most companies will refund your money.

Practices for Effective Testing

During the diet trial, it is imperative that the pet consume only the prescribed food. Any treats, table foods, OTC foods, chew toys with flavoring, and even flavored medications, including heartworm and flea prevention, can sabotage the trial. Everyone in the home must cooperate. Other pets in the home must be fed separately or fed the therapeutic diet. Some owners don’t understand why the pet can’t have “just a little” something extra. I always explain it this way—if you are allergic to peanuts and someone slips “just a little” peanut product into something you eat, it will cause a reaction. It’s the same with your pet.

After Testing

If the diet is successful, you can confirm a food allergy by returning to the pet’s original food. Itching will resume within 14 days. Most people, however, don’t want to rock the boat if the pet is doing well, and opt to stay on the new diet. If the animal is doing well, you can also try adding in additional protein sources, one at a time, with the therapeutic diet, to more specifically identify offending foods. If the animal starts itching within two weeks, this protein is one to which the pet is allergic. If not, this protein is safe to feed your pet.

Suppose the diet doesn’t work. What then? First, be sure the diet was strictly adhered to. If so, consider another trial with a different diet. Sometimes allergies can overlap. For example, a pet who is allergic to chicken might also be allergic to duck, or an animal allergic to beef might also be allergic to venison. Or the animal may simply not have a food allergy.

The Myth of a Hypoallergenic Diet

There is no such thing as a one-size fits all “hypoallergenic” diet. Sometimes finding the right diet for the patient is a matter of trial and error. Hills, Purina, and Royal Canin all make excellent therapeutic diet foods. There are a number of novel protein diets available, and choosing which one to try depends on what the animal has already been exposed to. If a dog has never eaten fish, for example, a salmon/potato diet might be a good first choice. In cats, a good choice might be rabbit/pea. Hydrolyzed protein diets may also be tried. In these foods, the protein source has been digested to smaller fragments, which are less likely to stimulate the immune system. However, some patients may still react to diets containing a hydrolyzed proteins to which they are allergic.

One food I particularly like is Royal Canin Ultamino, which is formulated for dogs with severe food sensitivities. The protein source is broken down to amino acids which can be absorbed without triggering an immune response. It can be used as a short-term elimination diet to rule in/out food allergies. It can also be fed long term. There is also a Royal Canin Ultamino for cats. Remember the therapeutic diets require a veterinary prescription.

Where allergies are concerned, it is always best to formulate a plan with your veterinarian in order to achieve the best outcome. Allergies can be frustrating, expensive, and time consuming, but with patience and perseverance, are generally manageable.

Ellen Fannon
Ellen Fannon
Ellen has been making up stories since before she could write. Ellen is a practicing veterinarian, former missionary, foster parent, pastor’s wife, and church pianist/organist. She originated and wrote a newspaper column on pet care for six years before taking an assignment with the Southern Baptist International Mission Board. She lives in Valparaiso, Florida with her husband, son, and assorted pets.

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