Food Allergy May Be The Cause Of An Itching Pet

Food Allergy May Be The Cause of An Itching Pet

Pruritis, the medical term for itching, is a very common complaint at vet clinics across the country, particularly here in the Southeast.  Although uncommon (about 10% of allergic patients have a food allergy), it tends to attract a lot of attention from owners and pet food marketers.  In this article I’ll try to unravel some of the mystery and misinformation surrounding this condition.

An allergy is a hypersensitivity disorder involving the immune system.  In other words, the body’s system responsible for fighting infection is triggered in response to something other than potential infection.  In the case of food, it can be a protein, carbohydrate, or food additive that triggers the response.

The most common symptoms of food allergy in pets include non-seasonal itching and recurrent skin and ear infections.  There are other conditions that can cause these symptoms such as atopy (environmental allergy), flea hypersensitivity, drug reactions, mites, dermatophytosis (ringworm), or behavioral disorders.  Your veterinarian will likely recommend testing to help rule in or rule out these conditions prior to testing for food allergy specifically.  There can also be overlap among these conditions.  For example, 20-30% of pets with food allergy also have environmental or flea allergy.

Pets can be allergic to any ingredient in the diet.  The most common offenders are beef, dairy products, lamb, chicken, egg, soy, and wheat.  Pets can be experiencing food allergy even on a grain-free diet.  While a grain-free diet does eliminate wheat and other grains, it still contains many other potential allergens.  In fact, beef and dairy products have been found to be more common causes of food allergy than wheat in several studies.

It does not take a large amount of an ingredient to trigger a reaction.  For example, a treat containing chicken could be enough to trigger a reaction in a pet eating an otherwise poultry-free diet.

Testing for food allergy is straightforward and involves a food trial.  A food trial is when a food containing a single, highly digestible protein source is fed exclusively for 8-12 weeks.  This means no additional treats or even flavored medications can be given.  Another potential food choice for a trial is a food in which the proteins have been “hydrolyzed,” or broken down into pieces thought too small to be recognized by the immune system.  Your veterinarian may have a preference for which particular diet to use in a food trial.

After 8-12 weeks, the symptoms should have improved.  At this time, a single protein, wheat gluten for example, is added for 2 weeks to check for an allergic reaction.  If no reaction, another protein is added.  Any allergic reaction is used to diagnose a food allergy.

Over the counter diets labeled as containing specific meats have been repeatedly found to be contaminated with other protein sources in several studies.  So although a pet is eating a diet labeled as containing only venison, it likely contains trace amounts of other meats, making it not suitable for an effective food trial.  The quality control required to prevent contamination is part of what makes veterinary-exclusive diets more expensive.

The prognosis for a food allergy is excellent if the offending ingredient can be identified and eliminated which requires time and patience.  Always be wary of claims made on pet food labels.  They are often designed to attract rather than inform consumers.

-Dr. Ian Birkbeck

Dr. Birkbeck writes monthly columns for the local publication, “The Viera Voice”.  If you have any pet medical questions you’d like to see answered in a future column, you can email them to

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