Healthy Paws: Hypoallergenic Diets

Editor’s Note: Healthy Paws is a column sponsored and written by the owners of Clarendon Animal Care, a full-service, general practice veterinary clinic. The clinic is located 3000 10th Street N., Suite B. and can be reached at 703-997-9776.

Does your pet have chronic or intermittent diarrhea, but otherwise feels great? Does he or she itch and scratch constantly, have hair loss, repeated skin infections, ear infections or rashes? If you answered yes, read on, as your pet could possibly have a food allergy.

What are the most common food allergies?

Contrary to all the pet-food company marketing, it is rarely grains! The vast, vast majority of the time, the allergy is to the animal protein source, with chicken being the most common, and then beef.

What’s the difference between a food allergy and a food sensitivity?

An allergy implies that the body’s immune system is involved in the symptoms; whereas food sensitivities can cause similar but often milder symptoms that are due to a local reaction in the GI tract (think lactose intolerance in people). A food sensitivity may improve simply with a diet change to a new brand or variety, whereas a food allergy is related to the body being sensitized via the immune system to a specific ingredient.

How is a food allergy diagnosed?

Unfortunately, a true food allergy can be difficult to definitively diagnose. There is no accurate blood test for food allergies (though Dr. Google may suggest otherwise), and the only way to really diagnose a food allergy is to do a STRICT trial with a hypoallergenic or hydrolyzed diet for 8-12 weeks. Because it can take days to weeks for an offending protein to fully be eliminated from the body, and also significant time for the GI tract to heal following insult, the full 8-12 weeks is vital to ensure we allow enough time to see clinical improvement if it is going to happen!

Not only that, in order to make a truly definitive diagnosis, at the conclusion of the food trial one must reintroduce the original food to see if the symptoms return! Understandably, many owners are reluctant to go this final step if their pet’s symptoms are significantly improved, but without it we do not know if improvement was just a coincidence (or perhaps due to some other treatments that may have been initiated at the same time or a changing of seasons).

Essentially, a food trial is a diagnostic test — but one that takes 8-12 weeks to get results.

What make a diet hypoallergenic?

A hypoallergenic diet is designed to be absent of the ingredients most likely to trigger a true allergic response. Again, protein sources are much more likely to be the culprit than grain or other ingredients. There are two ways to address this protein issue — one is with a “novel” protein — i.e. a protein that the patient has never been exposed to previously — and the other is with a “hydrolyzed” protein — i.e. a protein that is broken down into such small pieces during the manufacturing process that it is not recognized as foreign by the body.

A thorough dietary history is very important when figuring out which hypoallergenic diet route to go. If the pet has been exposed to a variety of protein sources throughout their life, a hydrolyzed diet may be a better option.

It is important to note that many of the over-the-counter (OTC) diets that may tout themselves as being lamb, bison, turkey, etc. actually do have chicken further down the ingredient list. OTC diets are frequently contaminated with minuscule amounts of non-ingredient proteins as well. Thus, for the purposes of a strict food trial, we are more apt to recommend a prescription diet that is strictly controlled in the manufacturing process and is guaranteed to be a single protein source. In a very sensitive pet, even having a trace of the offending protein (such as, may remain if there was not strict cleansing of the equipment between processing of different diet varieties) could be enough to trigger symptoms. There are a limited number of OTC options that may be viable alternatives to a prescription diet, but these should be discussed with and approved by your pet’s veterinarian prior to going to the effort of a full food trial with them, as in some cases they may not be sufficiently “hypoallergenic.”

This sounds hard!  

There’s no arguing that a strict food trial requires some restraint and diligence on the part of the owner! Treats play an important role in our relationship with our pets, and having to be really strict can be tough…but it important to remember that it’s for a relatively short period of time and that eventually you will be able to slowly reintroduce things into your pet’s diet.

It is also important that all members of the family be on board with a food trial before it’s initiated — again, all it takes is a single exposure to the offending protein to set things back to the beginning!

Good news — you finished the food trial and your pet’s symptoms are improved. Now what?

At this point, we’d typically recommend SLOWLY reintroducing things back into your pet’s diet, but still being sure to avoid the suspected offending protein — i.e. each week, add one new item back into the diet, monitoring for recurrence of the original symptoms.

Bad news — you finished the food trial and your pet’s symptoms are not improved. Now what?  

Fret not — all is not lost! You’ve still gleaned some very valuable information by ruling out a food allergy. In the case of skin symptoms, environmental allergies may be a factor and in the case of GI symptoms, a whole plethora of other possibilities remain. It will be important to work with your pet’s veterinarian to continue looking for the cause of chronic skin or GI symptoms.