Food Allergy/Intolerance

Food Allergies






(Only some of the captioned signs are usually present in a given animal, not necessarily all.)Allergic dog

The classical canine food allergy lesion distribution includes signs of facial itching, foot or limb chewing, belly itching, and recurrent ear infections.


Your Pet's Itchy Skin

Itchy skin in the small animal is often more than just a minor annoyance. Red, oozing bald patches, rashes, and large expanses of hair loss are unfortunate markers of very real discomfort for which a cause should be sought and specificAllergic cat

In cats, food allergy usually produces scabs and other signs of itching around the face or neck.

ally dealt with.

The food allergy is one of the itchiest conditions known to cat and dog. Animals eat a variety of processed food proteins, fillers, and colorings which are further processed inside their bodies. Proteins may be combined or changed into substances recognized by the immune system as foreign invaders to be attacked. The resulting inflammation may target the GI tract or other organ systems but, in dogs and cats, it is the skin that most often suffers from this immunologic activity.

Many people erroneously assume itching due to food allergy requires a recent diet change of some sort. In fact, the opposite is true.

Food allergy requires time to develop; most animals have been eating the offending food for years with no trouble.

What Kind of Allergy?

Sarcoptic mange and inhalant allergy (also known as atopy) are the two conditions which must be distinguished from food allergy as the treatment approach to each is markedly different. Much time and money can be wasted pursuing the wrong the problem.

Please consider the following clues which contribute to pointing us towards the food allergy as a diagnosis. Your pet demonstrates:

Your pet has been treated for sarcoptic mange without any positive change.
Your pet's itchiness is not and has never been a seasonal problem.
Your pet has responded poorly or only partially to cortisone-type medications.
Your pet has had a skin biopsy demonstrating changes often associated with allergy or, more specifically, food allergy.
A lesion distribution pattern which is common for food allergy (see illustration at top of page)

Please note that three of the above four criteria relate to what you, the owner, observe at home. Trouble results when the veterinarian must speak to different family members about the pet and there is disagreement in their observation of the pet at home. It is best to have one person, preferably the one who has the most contact with the pet, be the spokesperson and make the relevant judgments.

The Flea Factor

Some animals have many allergies. It would not be particularly unusual for an animal with a food or inhalant allergyFlea



to also be allergic to flea bites, especially considering that flea bite allergy is an extremely common allergy among pets. Because allergies add to each other, it is possible that a food allergic dog will not itch if its fleas are controlled. Since new technology has made flea control safe and convenient, it is especially important (and no longer difficult) to see that fleas are not complicating a pet's itching problem.

Ensure immaculate flea control for any itchy pet!

For more information on flea biology and flea control, visit the special site prepared by the Iowa State Veterinary College: http://www.vetmed.iastate.edu/services/vth/clinical/derm/flea/

How to Deal with the Food Allergy Suspect: The Hypoallergenic Diet Trial

The Basic Principle

To determine whether or not a food allergy or intolerance is causing the skin problem, a hypoallergenic diet is fed for a set period of time. If the pet recovers, the original diet is fed for up to two weeks to see if itching resumes. If we see recovery with the test diet and itch with the original diet, then food allergy is diagnosed and the pet is returned to either the test diet or another appropriate commercial food indefinitely.

What Is a Good Hypoallergenic Diet?

There are two approaches to this question. Obviously, the test diet must be of a food source that the patient could not possibly be allergic to. The traditional method is the use of a novel protein and carbohydrate source; that is, something the pet has never eaten before. In the past, lamb has been the protein source of choice as American pet food companies had traditionally failed to produce lamb-based pet foods. Unfortunately, recent production of lamb and rice-based foods has removed lamb from the acceptable hypoallergenic diet list.

Fortunately, many pet food companies have discerned the need for diets using unusual protein and carbohydrate sources with a minimum of additives. Foods can be obtained based on venison and potato, fish and potato, egg and rice, duck and pea, and even kangaroo. Our hospital generally recommends duck and potato based foods for dogs and duck and pea based foods for cats. We have chosen these products because they are available both as canned as well as dry formulas. (Most pet owners prefer to feed a combination of dry and canned food.)

It is important that during the diet trial no unnecessary medications be given. No edible chew toys (such as rawhides or bones) should be given. Treats must be based on the same food sources as the test diet. (Beware of rice cakes, though, as wheat is commonly used as a filler.) Chewable heartworm preventives should be replaced with tablets.

Home cooking was originally the only option felt to be appropriately free of allergens but for most animals these special commercial foods are adequate. Occasionally home cooking ends up being necessary after all.

The Hydrolyzed Protein Method


Recently a new approach has been introduced using therapeutic diets made from hydrolyzed proteins. This means that a conventional protein source is used but the protein is broken down into molecules too small to excite the immune system.

How Long to Feed the Trial Diet

In the past, 4 weeks was thought to represent a complete trial period. More recent work has shown that some food allergic animals require 8 to 10 weeks to respond. This may be an extremely inconvenient period of time for home cooking. Our current recommendation calls for a recheck appointment or phone call after four weeks of diet trial and then again after eight weeks of trial. Eighty percent of food allergic dogs will have responded to diet trial at least partially by six weeks. The Labrador retriever and cocker spaniel appear to require up 10 weeks of trial diet before showing a response. Some animals may even require a longer period.

All commercial diets mentioned have a 100% guarantee. This means that if your pet doesn't like the food, the food can be returned for a complete refund (even if the bag is opened). This is especially helpful for feline patients, as cats are famous for being choosy about what they are willing to eat.


What to Do if the Diet is Successful?

To confirm food allergy, return to the original food; itching resumes within 14 days generally if food allergy was truly the reason for the itchy skin. Many people do not want to take a chance of returning to itching if the patient is doing well; it is not unreasonable to simply stay with the test diet if the pet remains free of symptoms.

It is possible to more specifically determine the identity of the offending foods after the pet is well. To do this, a pure protein source (such as cooked chicken, tofu, wheat flour or any other single food) is added to the test diet with each feeding. If the pet begins to itch within 2 weeks, then that protein source represents one of the pet's allergens. Return to the test diet until the itching stops and try another pure protein source. If no itching results after two weeks of feeding a test protein, the pet is not allergic to this protein.

What to Do if the Diet is Unsuccessful?

Generally, an unsuccessful food trial is strongly suggestive that an inhalant allergy is really the primary problem but there are some other considerations that should at least be mentioned: Are you certain that the dog received no other food or substances orally during the trial? Was sarcoptic mange ruled out? Your pet may require a longer diet trial. Are you certain regarding the factor that pointed us toward the food allergy? If your pet has not been biopsied, now may be a good time. If an inhalant allergy has risen to the top of the list, symptomatic relief either via medication, special baths, or allergy shots will likely be necessary. Chronic itchiness can be extremely uncomfortable and prompt relief is the goal.