POV (Point of View) Your family veterinarian at City by the Sea Vet suspects that your dog has a food allergy and would like you to change her diet. But what does this even mean? Below are some common statements and myths that I encounter often that will hopefully clear things up regarding food allergies and appropriate diet selection.
If this were true, I would order this test daily! There are several DIY tests that can be purchased online that request blood, saliva, or hair samples to be submitted to investigate food allergies. Despite the convenience factor, these tests have little merit. There are several studies that debunk this myth, but my favorite study was performed in 2018.1 The fur of three groups of dogs and cats were enrolled in this study: healthy, allergic, and fake/plush toys. That’s right- think of the toy that you just won on the boardwalk over the weekend enrolled in the study. The results revealed that all three groups of patients were clinically indistinguishable: meaning that a plush toy showed comparable results to the allergic and presumed non-allergic dogs! In conclusion, a food elimination trial with a prescription novel or hydrolyzed diet selected by your veterinarian at City by the Sea Vet is the ONLY way to investigate food allergies in dogs and cats. These diets are specially formulated to sneak past the immune system and are less likely to cause a skin response. The duration is usually 8-12 weeks of this diet with no exceptions. Careful consideration must be taken with flavored medications, toothpastes, supplements, and flea/tick heartworm prevention. I like referencing these discharge instructions from Avacta Animal Health: Canine_Food_Trial.pdf (avactaanimalhealth.com)
When I hear a statement like this, here are some questions to think about:
If a food allergy is suspected by your primary care veterinarian, the first step is to discuss where to obtain an appropriate diet. There are many over the counter diets with many flash words like “grain- free,” “limited-ingredient,” or “hypoallergenic.” However, there are several studies that show although these diets claim to be pure, they could have several contaminants of common food allergens.2 My approach is to start from a clean slate and to select a prescription hydrolyzed/novel protein diet with your veterinarian. To name a few popular brands: Purina HA®, Royal Canin HP®, PW®, PR®, PD®, PV® or Hills Z/D®. Once the diet is selected, it helps to have a family pow-wow prior to starting the diet to ensure that everyone is on the same page that this must be fed exclusively for 8-12 weeks. It may be frustrating that your veterinarian is telling you to commit to another bag of dog food that is 2-3 times more expensive than a diet that is obtained “over-the-counter.” But eventually, this gets the veterinary team closer to a diagnosis, and less money spent on complications from allergies through the pet’s lifetime such as skin infections. If the food allergy trial is executed correctly and the pet is no longer itchy, you are off to a good start! Ideally, the last step is to re-challenge the pet with a single protein such as boiled chicken, turkey, or beef while still on this diet trial to see if itchy behavior returns. However, it would be acceptable to keep the patient on trial food since it is a balanced diet. If the pet is still itchy despite the food allergy trial, your veterinarian may discuss other reasons behind itchy behavior such as flea allergy, environmental allergy, hormonal imbalances (i.e. Hypothyroidism, Hyperadrenocorticism,) impaired skin barrier, or immune mediated disease.
There has been a recent push in pet food advertising that depicts grain and wheat to be common food allergens. However, it is more common to see dogs and cats allergic to meat proteins than carbohydrate sources. The most common reported food allergens in dogs and cats are chicken, beef, dairy, turkey, and fish, but can also include others like lamb, pork, eggs, and wheat.3 Traditionally, Irish Setters were the only breed reported to have a true gluten allergy, but a recent study performed in 2018 revealed that a population of Border Terriers with a gene mutation may be added to this list.4 , 5 A grain-free diet should only be recommended and monitored by a veterinarian due to the small risk of developing a specific heart disease called dilated cardiomyopathy; DCM.) The Food and Drug Administration has found a potential link to dogs eating grain-free diets with wheat substitute ingredients such as peas and lentils that may interfere with heart function leading to DCM. With that being said, a novel or hydrolyzed protein diet that is grain- inclusive is usually attempted first to avoid the DCM fiasco.6
Oral antihistamines have been around for decades and have their purpose for managing *some* skin conditions such as insect bites, mast cell tumors, and allergic reactions. However, the use of antihistamines to treat allergic itch secondary to food allergies is not validated. A group of veterinary dermatologists came together in 2015 to form a task force that ranked effective therapies for managing Atopic Dermatitis, A.K.A allergic skin disease secondary to environmental allergies. These folks characterized oral antihistamines into the “Interventions likely to be of little or no benefit to treat chronic canine atopic dermatitis.”7 Yikes. Furthermore, it is estimated that only and underwhelming 10-30% of dogs will only respond to oral anti histamines to relieve allergic itch with the appropriate dosage. Although this article discusses a different type of allergy in dog patients, this information can be applied to itchy dogs secondary to presumed food allergies. Check out Dr. Brianna Stafford’s article on this blog page too – she discusses environmental allergies more in depth.
Natalia Santos, D.V.M.