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The terms “food allergy” and “food intolerance” are often used interchangeably, but they are not the same. What are the differences and how are they diagnosed?

The Purina Institute provides the scientific facts to support your nutritional conversations.

In focus

Food allergies & food intolerances in pets

HOT TOPIC

An adverse food reaction is an abnormal response following the ingestion of a food or food additive. Food allergies and food intolerances are both types of adverse food reactions. A food allergy occurs when the pet’s immune system mounts a response to a specific food substance. With a food intolerance, the immune system is not involved.

In dogs and cats, immune-mediated reactions (true food allergies) are not common in practice, and the distinction between allergy and intolerance is rarely made.1 Therefore, the term “adverse food reaction” is widely accepted and used.

Food allergy or food intolerance:what is the difference?

Adverse FoodReactions

in Pets

Immunological

Non-immunological

Food Allergye.g. beef or

dairy allergy

Dietary Indiscretion

e.g. Scavenging

Food Intolerancee.g. lactose intolerance

or histamines in certain sh

Food Aversion

References1. Lloyd, D. (2006). Diagnosis and management of adverse food reactions in the dog. Proceedings of the World Congress WSAVA/FECAVA/CSAVA, Prague, Czech Republic, 232–235. 2. Rudinsky, A. J., Rowe, J. C., & Parker, V. J. (2018). Nutritional management of chronic enteropathies in dogs and cats. Journal of the American Veterinary Medical Association, 253(5), 570–578. doi:10.2460/javma.253.5.570

3. Gaschen, F. P., & Merchant, S. R. (2011). Adverse food reactions in dogs and cats. Veterinary Clinics of North America Small Animal Practice, 41(2), 361–379. doi:10.1016/j.cvsm.2011.02.0054. Verlinden, A., Hesta, A., Millet, S., & Janssens, G.P.J. (2006). Food allergy in dogs and cats: a review. Critical Reviews in Food Science and Nutrition, 46, 259–273. doi:10.1080/10408390591001117

5. Chandler, M. (2002). Essentials of nutrition in dogs and cats with gastrointestinal disease. Companion Animal Practice, 24, 528–533. doi:10.1136/inpract.24.9.5286. Mueller, R.S., & Unterer, S. (2018). Adverse food reactions: Pathogenesis, clinical signs, diagnosis, and alternatives to elimination diets. The Veterinary Journal, 236, 89–95. doi:10.1016/j.tvjl.2018.04.014

Clinical signs of food allergies and food intolerances in pets

RL/CRCR

Pets with food allergies commonly exhibit vomiting and diarrhea with concurrent dermatologic signs.2 Gastrointestinal signs associated with food allergies are often indistinguishable from those related to a food intolerance. Skin disease, however, is only associated with true food allergies.3

In dogs and cats, the most consistent clinical sign of food allergies is pruritus (itchy skin). This may be localized or generalized,4 but commonly affected areas include the ears, feet, groin and muzzle.

Prevalence of food allergies in pets

Currently, the best method for diagnosing a food allergy in dogs and cats is the “dietary elimination trial.” This involves feeding a diet without the suspected culprit ingredient, followed by a challenge (reintroduction of the suspected ingredient) after clinical signs have resolved.3 The elimination diet should only contain ingredients which the pet has not previously consumed. Elimination diets can be home-prepared or commercial diets e.g. “selected-protein” diets or hydrolyzed diets (hydrolyzed proteins are broken down so the body does not recognize or react to them).

The diet should be fed for at least 8–12 weeks in pets with dermatological signs.6 In pets with gastrointestinal signs, 2–4 weeks may be sufficient for clinical signs to resolve.4 A definitive diagnosis may take many months due to the time involved in re-challenging.3 Compliance is key to a successful dietary elimination trial, and it’s important to exclude all other protein sources including flavored supplements or medications, chew toys and treats.

The exact prevalence of food allergies in dogs and cats is unknown, and the diagnosis is uncommon.4 Even though skin problems are the primary clinical sign, food allergies are responsible for only around 1% of all skin diseases in dogs and cats.4

COMMON PET FOOD ALLERGENS4

Beef

Dairy

Wheat

Egg

Chicken

Diagnosing food allergies

Food allergies can occur at any age in dogs and cats.4 An allergic reaction does not occur on first exposure to a food;4 a previous exposure is required for the immune system to recognize the allergen. A food intolerance, however, can occur upon first ingestion. E.g. dogs with a lactose intolerance lack the enzyme lactase required to digest lactose (the milk sugar found in milk). If milk is consumed, diarrhea may result.

Unfortunately, there is no quick or easy way to confirm a food allergy in pets. Although blood, intradermal and patch testing methods are available, they are not validated1 and are generally not considered reliable for the diagnosis of a food allergy.6

A dietary elimination trial is the gold standard for diagnosing food allergies in pets

Food allergens are nearly always proteins. No food allergen is more allergenic than another. The most common pet food allergens are the proteins found most often in pet diets, which vary between countries.5

FlavoredPlastic Toys

Treats &Chews

Human Foods

What NOT to give during a dietary elimination trial:

Flavored Toothpastes

Flavored Medications

or Supplements

Rawhides

Only around 1%

of all skin conditions in dogs and cats are due to food allergies

Beef

Dairy

Fish

Poultry

Barley/Wheat