Food Allergies and Your Dog

Is your dog always scratching, particularly around his face, abdomen, anus and arm pits? Does he chew and lick his feet and legs? Does he have recurrent ear infections? Does he seem prone to hot spots and skin infections? He may have a food allergy. About 20 percent of all cases of itching and scratching in dogs are caused by food allergies alone. Food allergies should not be confused with food intolerance. The latter doesn't cause itchy skin, but more often diarrhea or vomiting.

But don't think your dog needs to have recently switched to a new diet in order to be allergic to some new food. In fact, the opposite is true. Because food allergies usually take time to develop, most dogs have been eating the food they become allergic to for years before signs appear. Although the process is not entirely understood, sensitization to a particular component in foods involves an antibody response that occurs in the intestinal tract. Although this sensitivity usually takes time to develop, food allergies can first appear in dogs as young as 5 months of age, and as old as 12 years, although most first appear between 2 and 6 years of age.

In general, the foods that are most often associated with food allergies are the most common ones in dog foods---in part simply because these are the foods dogs are exposed to the most. They are, in order of most common offenders: beef, dairy products, chicken, lamb, fish, chicken eggs, corn, wheat, and soy.

It's often hard to decide if a dog's itching is caused by a food allergy as opposed to an inhalant allergy. A dog with recurrent yeast infections of the ears, a dog that itches throughout the entire year, or a dog that does not respond to steroid treatment is more likely to have food than inhalant allergies. In addition, sarcoptic mange and flea allergies must be ruled out, as they can sometimes be confused with a food allergy.

Unfortunately, there is no reliable blood test or skin test for food allergy. At this time the only reliable test is a food trial in which the dog is fed a source of proteins and carbohydrates it has never before been fed, and eats only this diet for 12 weeks (veterinarians used to recommend 3-week trials but have more recently found dogs are more likely to respond when in12 weeks trials). Lamb and rice diets were at one time touted as hypoallergenic, but their merit was due to the fact that lamb was rarely fed to dogs in the United States at that time. So unless your dog has never eaten lamb before, it's a poor choice. Instead, food trial diet foods are usually made from sources your dog almost certainly has never eaten, such as venison or rabbit. Hydrolyzed protein diets are also used in food trials; in these foods the proteins are broken down into very small molecular sizes that don't elicit an allergic response. When on the food trial, it's imperative that the dog doesn't eat anything not specifically part of the diet. That means no chewable medications, no chewies, no flavored toothpastes, no flavored toys, no stolen bites from the other dog's bowl, no gravy from your sticky fingers, not even any kitty poop! For variety, you can slice the canned variety of the trial food and bake it to make crunchy cookies. If he does sneak an illicit snack, make a note of the date and what the food was. This will be important if he continues to have allergic responses.

Once the trial period is over, the dog is allowed to eat the original diet to see if the allergic reaction returns. Alternatively, components of the original diet are introduced back to the dog one by one until one elicits an allergic reaction. This is repeated until all the diet components that cause the reaction are identified.

You may need to keep your dog on a special diet for the rest of his life in order to avoid certain food types. Such diets are available from your veterinarian, or you can make homemade diets using recipes provided by your veterinarian.