Adverse Food Reactions

Adverse Food Reactions

Adverse Food Reactions

Adverse food reaction (AFR), food intolerance, and food allergy are terms often misused interchangeably to describe a pet's abnormal physical responses resulting from the ingestion of a food source. This also includes food flavoring, preservatives, or other food-like products. In most cases, allergy is technically a misnomer, though it helps people understand the severity of their pet's problem with food. A true allergy is based on an abnormal or overactive immunologic response, while an AFR is an abnormal response often based on other host factors not directly linked to the immune system; food appears to be the main trigger for the symptoms and treatment is geared toward avoidance of trigger foods. There are loads of different food allergies that people suffer with though. For example, some people might have a corn allergy or a chocolate allergy or even a perfume allergy.


Symptoms develop over time in most dogs -symptoms becoming noticeable a few years after a pet has been on a food source is not abnormal. Owners typically note symptoms related to skin or intestinal abnormalities. These can include: itchy skin, recurrent skin or ear infections, hair loss, thickened or scaly skin, intermittent vomiting or loose stools, rear-end scooting, bloody or mucousy stools, frequent bowel movements, and increased gas. Less commonly, symptoms related to other organ systems may also be noted.

Causes: Food vs Environment

Adverse food reactions and environmental allergies can produce nearly identical symptoms in animals which makes a diagnosis based on symptoms alone ill-advised. That's why owners need to educate themselves about allergy tests and use that as a starting point.

A few slight differences between the two sources about testing include:

1) Age at the first onset of symptoms

2) Seasonal signs vs year-round signs. Sometimes age and seasonal differences are useful, although even these slight differences do not hold true for every patient. Food and environmental sensitivities can also be co-occurring, making diagnosis more complex. Food products often linked to AFR contain beef, chicken, egg, dairy, and wheat; with new diets continuing to flood the market, the potential for AFR to originate in other sources is becoming more likely.


Since symptoms of AFR can mimic numerous conditions, diagnosis is made by a process of disease elimination and a corresponding food trial. First, infectious causes must be ruled out. If no infectious cause is determined, additional diagnostic blood work, xrays, fecal and urine testing can be useful in ruling out other causes for symptoms. Unfortunately, no diagnostic test currently available gives reliable results about true food intolerance.Testing for environmental allergies, however, is a very helpful diagnostic tool- especially if a pet is suspected to have both environmental and food sensitivities. Food Trial A food trial, when done through the recommendations of a veterinarian, is the best test after other common causes of symptoms have been eliminated. A food trial of a selected food will be made based off information a client provides on the pet's food history. This includes all foods, treats, flavored medications, chew toys, and supplements previous and presently consumed by the pet. Food sensitivity requires information about previous exposure, which is the knowledge vets use when selecting a diet for a food trial, as well as then being able to better choose the future manufacturer for treats and food that the dog will be able to enjoy and digest. Commercially available dog food (even those with limited ingredients) are rarely successful in food trials.

Standard dog foods do not have ingredient quality control. Prescription diets or home cooked diets are used in food trials. In the long run, one of these options will save money, time and frustration for all involved. After a diagnosis is confirmed, your pet may be able to slowly return to certain foods they previously enjoyed. A food trial typically lasts for 8-12 weeks- possibly longer if a pet does not tolerate the first food prescribed or if owner compliance is low. An AFR diagnosis is confirmed based on response and resolution of symptoms on the food trial followed by a recurrence of symptoms when the previous diet is reintroduced. During this time, all other health conditions must be managed. Progress exams will be needed throughout the trial for oversight.

Tidbits for Potentially AFR pet owners:

  • Gather a thorough written food history (with all ingredients and flavors) prior to your vet appointment, including common table scraps,treats from you or neighbors, medications, consumed prey, flavored toys, diet supplements, toothpaste etc. to help tailor a trial food program for your pet. Without a thorough history, it can take longer to find the right diet for your pet.
  • Dogs do not outgrow their food sensitivities. Once a specific food has been identified as a trigger, it will cause issue with each reexposure. Treat by avoidance.
  • Allergy medications seldom provide complete resolution of AFR symptoms yet may still have a place in treatment of symptoms.
  • Your pet may still have symptoms while on a food trial. Do not stop the food trial early without consulting with your vet.
  • It's helpful to have food trial "safe" treats. Usually the food the dog is on, or the canned version, can be used to make baked goodies or meatballs for your pet.
  • Home-cooked diets are usually not balanced nutritionally. If you plan to keep your dog on a home cooked diet long-term, consult a veterinary nutritionist.
  • Food intolerance can develop toward more than one food
  • Genetics appears to play a role in the dogs that develop food sensitivities. Retriever breeds are frequently diagnosed.

Many health conditions can be mitigated or alleviated through diet alterations. This is true of both humans and their animal companions. Quality nutrition in your pets can help save expense on veterinary visits, medications, and treatments in the future.

### Amanda Burow, D.V.M. (Dr. B), is a graduate of Iowa State University's College of Veterinary Medicine. Dr. Burow's patient list includes hunting dogs of all varieties, as well as several field trial dogs and full time sporting guide dogs. In addition to practicing general veterinary medicine, she has special interest in the areas of preventive care, emergency medicine, and dermatology. In her spare time, she enjoys being outdoors and on the lake, staying active, reading, and spending time with family and friends. Mud River is proud to share these tips from Dr. B with our customers. Keep in mind it is best to work with your local veterinarian to determine the needs for your animals.