Merriam-Webster defines "hypoallergenic" as "having little likelihood of causing an allergic response." Easy enough? Unfortunately, no.
When it comes to dogs, there is great variation between what ingredients are likely to cause an allergic reaction in one individual versus another. For example, lamb has often been thought of as a "hypoallergenic" protein source for dogs, but in a review of 278 cases of canine food allergies, 13 dogs were determined to be allergic to lamb. Thirteen out of 278 (5%) may not sound like a big problem, but to put it in context, fewer dogs were allergic to corn (7), pork (7), fish (6), and rice (5). So, for dogs that are not allergic to lamb, a lamb-based diet is indeed "hypoallergenic," but if yours happens to be a member of the 5%, it is anything but.
Let’s look at the study in another way. The most allergenic ingredient was beef (95 cases), meaning that about one-third of dogs with food allergies are allergic to beef. So, beef can’t be hypoallergenic, can it? Well, for the two-thirds of dogs who are not allergic to beef, that’s exactly what it is.
Most veterinarians now do not recommend feeding potentially food-allergic dogs diets containing such commonly used ingredients as either lamb or beef. Instead, we often rely on limited ingredient diets made from weird protein and carbohydrate sources like duck, venison and sweet potato. I haven’t had the greatest of luck in managing food allergic dogs with these types of diets, however. Most of the time, I suspect treatment failures occur because the dogs are sneaking (or being snuck) small amounts of food that contain ingredients to which they are allergic. I wouldn’t be surprised, however, to find out that some dogs are developing allergies to “novel” ingredients that used to be out of the ordinary but are now becoming an increasingly common component of pet foods.
If any individual dog can, hypothetically speaking, be allergic to any protein source, novel-ingredient foods can’t really be considered nonallergenic, and even those thought to be hypoallergenic may incite an allergic reaction in a particular patient. For these reasons, I don’t refer to novel or limited ingredient foods as hypoallergenic.
I consider other products that take a different approach to be truly hypoallergenic. Several pet food manufacturers produce "hydrolyzed" diets made from proteins that have been split into such tiny pieces that the immune system does not mount an allergic reaction against them. The carbohydrate source and other ingredients that are included are also very unlikely to stimulate the immune system. While nothing in veterinary medicine ever works in all patients, I’ve had much better luck diagnosing and managing food allergies in dogs since I’ve started relying more on hydrolyzed foods and using novel/limited ingredient foods in a backup role.
If you’ve had trouble managing a food-allergic dog, ask your veterinarian if a hydrolyzed diet could be an appropriate option or you.
Dr. Jennifer Coates