Dr. Dorothy Laflamme: Food allergy can be a challenging condition for veterinarians to both diagnose and manage. Through this roundtable, we hope
to provide practicing veterinarians with a better understanding of how to recognize food allergies and food intolerance in
both cats and dogs, as well as how to help manage the condition through diet. In addition, we want to give veterinarians a
better understanding of the benefits of hydrolyzed diets, for both food-allergic and other patients.
Identifying food allergy and food intolerance
Dr. Laflamme: Because a high percentage of patients with food allergy and intolerance have both gastrointestinal and dermatologic clinical
signs, our panel includes specialists in both fields, as well as a feline practitioner to provide a focused perspective on
food allergy in cats. Our first question for the panel: Based on your clinical experience, for which patients do you put food
allergy high on your list of differential diagnoses?
Dr. Robert Kennis: For the most part, a food-allergic patient is a dog that presents with nonseasonal intense pruritus. The distribution pattern—face,
feet, ears, axillae, forelegs, and inguinal area—is consistent with an atopic dog, so there is significant overlap. Age of
onset is another key factor because atopic patients are usually 1 to 3 years old at onset, whereas the food-allergic patient
may be very young, less than 1 year old, or much older. Recurrent infections, recurrent otitis, and a poor response to therapy
suggest food allergy.
Dr. Elizabeth J. Colleran: For cats, I'll look for a food allergy in a young patient with facial pruritus or lesions around the neck. Eosinophilic granulomas
are also very common. There is certainly a different distribution pattern of skin lesions in cats.
Elizabeth J. Colleran
Dr. Stanley L. Marks: From a gastrointestinal standpoint, I am suspicious of food allergy in a patient that shows either acute or chronic manifestations
of gastrointestinal disease (vomiting, diarrhea, abdominal pain) in association with the feeding of a particular diet or diet
component. It is challenging to differentiate food allergy from food intolerance in these animals; however, the presence of
concurrent dermatologic disease manifested with pruritus in a younger animal makes food allergy more likely.
Stanley L. Marks
Dr. Nolie Parnell: If a dog is less than 2 years old with a history of chronic gastrointestinal disease and is otherwise stable, I'm concerned
about food allergy. Often, there is some type of dermatologic abnormality.
Dr. Kenneth W. Simpson: For cats, I lump together concurrent gastrointestinal and skin signs and maybe eosinophilia. This was demonstrated in a New
Zealand study involving 55 cats with pruritus and gastrointestinal complaints.1 Almost half of those cats (27) responded to food trials. Interestingly, adverse reactions to cereal were more common in
these cats than adverse reactions to animal proteins.1 That's been a somewhat similar experience in dogs diagnosed with food intolerance. In Karen Allenspach's paper,2 of 70 dogs with chronic enteropathies, about half responded to an elimination diet, and of those, most did not relapse when
challenged with the original diet. Even when the dogs were challenged with foods thought to provoke an allergic response,
such as beef, chicken, and milk, none of them had adverse signs.
Kenneth W. Simpson
Dr. Parnell: Obviously if the animal comes in and has extensive hair loss, that's a great sign. But if they are just licking their feet
and you don't ask the right questions, you may miss some subtle signs. I ask about licking of the paws, rubbing of the face,
and evidence of otitis. I look interdigitally to see if there is any evidence of excessive licking or excoriation.
Dr. Kennis: If you ask your client, "Does your dog itch?" the perception is that you mean physical scratching. But licking, biting, chewing,
and face rubbing are very common.
Dr. Simpson: There is no universal predictor as to which patient will be diet responsive; but if there are concurrent gastrointestinal
and skin signs, food allergy is at the top of the list of possibilities.
Dr. Marks: I would be much more suspicious of food allergy in a patient with diarrhea, vomiting, or colic when that patient has a concurrent
dermatopathy characterized by pruritus.
Dr. Kennis: How do we prove that it's truly allergic? Would you say that a case that relapses with provocative challenge is allergic?
Or do you still need to define it based on histopathology?
Dr. Laflamme: When we do a challenge, we don't know if it is truly an allergy. Whether it is immune-mediated or non-immune-mediated, they
can have the same clinical signs and the same response to diet. So the term "intolerance" is more appropriate. Intolerance
would include allergies, but it could also include all the other unknown mechanisms that cause an adverse reaction to food.
Many practitioners send out blood samples for blood testing to try to diagnose food allergy. How well do those assays work?
Dr. Kennis: There have been several reports indicating that IgE serum testing or skin testing is worthless for ruling in a food allergy.
Some laboratories even have a disclaimer that says the test has not been validated in several studies.