Food Allergy and Food Intolerance in Dogs

Allergies aren't fun for anyone, especially not for your dog who can't tell you what's making him so sick. If your dog vomits frequently, has diarrhea, irritated, itchy skin, a poor coat condition and/or hair loss, then he may have a food allergy.

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.

Allergic reactions are most commonly associated with protein sources - usually the meat in your dog's food. If your dog has an allergic reaction to a certain meat, you may want to try a food with a different protein source, such as – duck, venison, lamb, fish, etc.

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 we see recovery with the test diet then food allergy is diagnosed and the pet stays on either the test diet or another appropriate diet 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. 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 productions of lamb and rice-based foods have removed lamb from the "acceptable hypoallergenic diet" list.

Fortunately, many pet food companies have discerned the need for diets using unusual protein & carbohydrate sources with a minimum of additives. Foods can be obtained based on venison and potato, fish and potato, duck and potato, and even rabbit.

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.

The Hydrolyzed Protein Method

Recently a new approach has been introduced using 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. There are three such diets currently marketed. We have seen the best results from Hill’s Z/D and Ultra Z/D diets.

How long to feed the trial diet?

In the past, four weeks was thought to represent a complete trial period. More recent work has shown that some food allergic animals require eight to ten weeks to respond. We recommend that you schedule a recheck appointment 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. 

What to do if the diet is successful?

Simply stay with the test diet as long as the pet remains free of any allergy symptoms.

What to do if the diet is not successful?

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. 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 our goal as well as yours.

For an accurate diagnosis and treatment plan, always consult your veterinarian.