Glossary

Food allergy

An immune reaction to a protein in the diet that usually causes itchy skin and ear problems, and sometimes digestive upset.

Also called: dog food allergy, food hypersensitivity, adverse food reaction, itchy dog food, elimination diet

A food allergy is an immune reaction to something in the diet, nearly always a protein. Beef, dairy, chicken and wheat are among the most common culprits, simply because dogs eat them often. The usual signs are year-round itching, paw licking, face rubbing and recurring ear infections. Some dogs also have loose stools or vomiting.

It looks much like environmental allergy, and the two often occur together. Blood and saliva tests sold for food allergy are unreliable. The accepted method is an elimination diet trial, in which the dog eats only a novel or hydrolyzed diet for about eight to twelve weeks, with no treats, flavored supplements or chews, and then is rechallenged.

True food allergy is less common than many owners think. See a vet before switching foods, since fleas, atopy and infections must be ruled out first.

Last reviewed November 8, 2026

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Related terms

Food intolerance A non-immune bad reaction to a food, usually showing as vomiting, gas or loose stool, which differs from a true food allergy. Atopic dermatitis An inherited tendency to develop itchy skin and ear disease from allergens in the environment such as pollen, dust mites and molds. Limited-ingredient diet A food built around one protein and one carbohydrate source to reduce exposure, often used to look for a food allergy. Hydrolyzed protein diet A veterinary diet whose proteins are chopped into pieces too small for the immune system to recognize, used to diagnose and manage food allergy.