Food Allergy and Hypersensitivity in Dogs
Michael W. Stephan, D.V.M.
Juno Beach Animal Hospital
Food allergy or hypersensitivity is defined as an exaggerated response of the dog's immune system to a FOREIGN PROTEIN.
Approximately 30% of US dogs suffer from allergies. It is estimated that 5% to 10% of allergic dogs have food allergies. Food allergic dogs may also suffer from atopy (inhalant allergies), insect hypersensitivity (flea allergy), or contact allergies, or may be only food allergic. Allergies are genetic and can be passed on to the next generation in breeding dogs.
Signs of food allergy include: dermatitis, hives, otitis, vomiting, frequent defecation, soft stools, inflammatory bowel disease, malnutrition (low body weight, poor hair coat), poor appetite, and seizures.
Dermatitis may be either whole body pruritis (itching), or limited to scratching at the ears or licking the feet. At the time of presentation (to your favorite veterinarian) there may be a secondary staph or yeast infection. Allergy and infection can only be differentiated by microscopic examination of samples from the skin. The most diagnostic samples come from intact pustules (pimples) on the skin. The pustule is opened, the cells collected on a glass slide, then stained and examined through a microscope.
DO NOT BATHE YOUR DOG FOR AT LEAST THREE DAYS BEFORE A SKIN EVALUATION!
2. Diagnosis of Food Allergy.
It ain't easy!
There is no definitive test for food allergy. Allergies often present with similar signs, are usually chronic, and often have secondary diseases by the time we see them.
Intradermal skin testing or blood allergy testing are accurate for atopy BUT have no correlation with food allergy!
- The only accurate way to diagnose a food allergy is by doing a food elimination trial.
- Food allergies can develop to any PROTEIN in your dog's diet. When it comes to allergies, there is no such thing as 'good' protein or 'bad' protein.
- A food elimination trial is done by feeding your dog a NOVEL protein for 12 weeks.
NOTHING except for the selected diet and water should be given to your dog during the food trial.
Other sources of protein include (but are not limited to): Chew toys (raw hides, bully sticks, chewable medications (including heartworm preventatives), cookies, table (people) food, peanut butter, cheese, 'litter fritters' or other animal's feces, 'road kill', etc.
- Home cooking is the best form of food trial, though commercial diets are a close second.
- Challenge with the original diet should be done at the end of the food trial.
- New foods may be presented at the end of the food trial at the rate of 1 new food per week. Allergic reactions will usually be seen within 48 hours of the introduction of an allergen and may last for up to 5 days.
3. Definitions and Reading Dog Food Labels
Natural - There is no FDA or USDA definition for 'natural'
AAFCO - Association of American Feed Control Officials, Officials from USDA, FDA, and the pet food industry. Sets standards and guidelines but has no regulatory powers.
AAFCO Tested - indicates that the food has been fed to a group of dogs for a period of at least 6 months with blood work performed at the beginning and end of the trial to evaluate the effects of the diet.
AAFCO compliant - formulated to meet the AAFCO standards, but not tested as above.
Hypoallergenic - not likely to cause an allergic reaction. This term has no practical meaning in food labeling as there is no true hypoallergenic protein.
Hydrolyzed - a chemical process that splits protein molecules into smaller pieces in hopes of avoiding detection by the immune system.
Meat - skeletal muscle. Think steaks, roasts, etc. Unless specified, may be of any animal origin - beef, pork, lamb, chicken, turkey, duck, rabbit, etc.
Meat "by-product" - Non skeletal muscle exclusive of hide, hair, hoof, and horn. In other words, the rest of the animal - heart, intestines, lungs, organ meat. This term has gotten a bad rap, but there is nothing wrong with "by-product". It is a good source of protein and is mostly the parts of the carcass that we throw away but is consumed in poorer countries.
Meat "digest" - the rendered remains of the carcass. What happens to the turkey carcass the day after Thanksgiving for making soup. This is another good source of protein. Rendering also removes any bacterial or viral contamination.
Ingredient substitution - FDA allows the substitution of any ingredient for up to 6 months without changing the label.