Our pet of the month for November is Ginny! She is a young dog who was diagnosed with a food allergy. Ginny’s food allergy was causing repeated ear infections and itchy skin.
Food allergies are caused by an abnormal immunologic response to a harmless ingested protein. In dogs, food allergies most often cause itchy skin and ears. This can lead to secondary infections of the skin and ears.
In order to be allergic to a particular protein, a dog must be repeatedly exposed. Most dogs have ingested the protein they are allergic to, for months to years prior to developing an allergy. It is highly unlikely that a dog would be allergic to a protein they have never eaten before. That being said, there are cross reactions between different proteins. This means that a dog can have a reaction to a particular protein even if they have never eaten it before. Proteins that we know can cross react are (chicken, duck, turkey), (beef, milk, lamb) and (chicken, fish). The most common food allergens in dogs are beef, chicken, lamb and wheat.
When do we suspect a dog has a food allergy?
Any dog that has repeated ear and/or skin infections, anal glad infections/impactions and itching. It is impossible to distinguish between a food allergic dog and a dog with inhalant allergies (Atopy) based on symptoms alone. Veterinarians tend to be more suspicious of a food allergy if there are gastrointestinal symptoms as well as dermatologic symptoms, non-seasonal itching, and/or the symptoms started under 1 year of age.
The only way to diagnose a food allergy is to do a diet trial. A diet trial is when the diet is changed to a hypoallergenic diet.
There are different options for hypoallergenic diets.
- Novel Protein Diet: This is a new or novel protein source that the dog have never had before. Rabbit is a common novel protein used, but this could be chicken if the dog has never had chicken or poultry before.
- Hydrolyzed Protein Diet: This is a diet where the protein is broken down or predigested into small fragments that the body should not react to. We say “should” as there have been animals that have had reactions to even very small hydrolyzed proteins.
- There is a new diet released in October 2021 that was built from the ground up from amino acids. Remember our body breaks down protein sources so it can use amino acids. This means this diet has no proteins that the body should be reacting to.
A diet trial must be done for at least three months to clear the body of any past protein exposure. After three months, a food challenge can be done, where the suspected food allergen is fed again, to see if the patient reacts. Food allergic dogs will start itching within a few hours up to 10 days after the food challenge if they are allergic to that particular food item. A food challenge can be repeated for each protein source to specifically identify each protein the dog is reacting to. Without a food challenge, we cannot definitively diagnose a food allergy. If after 10 days of a food challenge, the dog has no symptoms, then a food allergy to that item is unlikely. In that case, inhalant allergies are more likely causing the dog’s symptoms.
When doing a food trial, it is important to use a prescription hypoallergenic diet or home cook. Over the counter dog foods can have traces of other protein sources that the dog could be reacting to which leads to confusion in interpreting the dog’s responses.
There are blood tests for food allergy available on the market. However, these are very inaccurate and a food allergy cannot be diagnosed or ruled out based on this. A food trial is the only way to diagnose a food allergy.
Prior to doing a food trial it is very important that the dog is on excellent flea control and that the skin/ear infections are treated. Both of these will cause continued itching, even if the underlying food allergy is treated.
In Ginny’s case, we controlled her ear and skin infections with topical medications and shampoos. We ensured she was on excellent flea control, then Ginny’s food trial was conducted with a hydrolyzed protein diet. Ginny improved significantly and shortly after her food challenge, she started itching again. A diagnosis of food allergy was confirmed and as long as she stays on her prescription food, her symptoms should be well controlled.
If you think your dog, or cat, may be experiencing symptoms of an allergy, please call Hawthorne Hills Veterinary Hospital and make an appointment. Our team is here to help!
Food Allergies in Dogs & Cats – VeterinaryPartner.com
What Every Pet Owner Should Know About Food Allergies – Cummings Veterinary Medical Center Tufts University
Research Update: Testing for Food Allergies – Tufts University
UC Davis Veterinary Medicine – Nutrition Service
American College of Veterinary Nutrition
American College of Veterinary Dermatology – Information for Pet Owners