The most common foods that dogs are allergic to are said to be beef, wheat, and dairy. In fact, a food allergy develops as the result of an immune system response. The immune system decides that a certain protein is an enemy, and it goes about dealing with it by releasing histamine and other chemicals into circulation on a search and destroy mission. In order for this to happen, the body needs to identify the allergen first, so the foods that are most likely to be allergens are simply the ones the dog has been exposed to in the past. Beef, wheat and dairy may be perfectly fine for a dog that’s eaten nothing but fish and sweet potato in the past because all three foods are new, and the body hasn’t decided to wage chemical warfare.
One of the most important things the immune system does is learn what is foreign and what is “self” Obviously, foreign invaders such as a bacteria must be attacked, while the body itself should never be attacked. In some dogs (and people), the immune system manages to become confused, and triggers an attack on an organ, or a protein that’s foreign such as the protein in beef, chicken, etc., and pollens. There’s a school of thought that suggests we should feed a variety of protein sources while the dog is young, so the immune system learns (so-to-speak) that this is food aka “Ok to ignore – don’t attack”.
My experience points me to think otherwise. Over the years, I’ve seen very big problems in many dogs that were fed everything but the kitchen sink. Those who become allergic to foods tend to do so with every single food they’ve been fed in the past. Their immune systems don’t wake up on a Monday morning and decide that chicken isn’t good any longer. Instead, they’re unable to tolerate chicken, beef, lamb, fish, venison…anything and everything they’ve ever eaten. The reason I say this is a very big problem is because in some cases, the only foods left are so expensive, or not available at all times that there’s nothing left to feed. I had one such case that stands above all others. Long story short, the dog weighs 87 pounds and had been fed just about any meat-protein sources you can think of – even beaver! The owner has a friend with a restaurant business who can get frog’s legs at wholesale prices. Imagine the expense of having to feed this to an 87 pound dog, and you see my point when I say that reserving a few foods is a good idea when feeding your dog. Keeping the less expensive options open by avoiding the feeding of turkey and beef, for instance, can make all the difference in the long run.
There’s another theory that’s sometimes presented as a fact, and that is that a dog allergic to say, chicken, may not be allergic to fresh chicken. That is, chicken in dog food may be a problem, but fresh chicken isn’t. The immune system recognizes the protein in chicken no matter how it’s served, be it in kibble, raw, or cooked. A dog that reacts to a kibble formulation can have that reaction to any of the foods in the kibble, and since almost all formulations include far more than chicken, you aren’t likely to be able to point to one item with certainty. Rest assured that if chicken (in this example) is tolerated, this wasn’t what the dog reacted to when eating a chicken-based canned or kibble diet.
When dealing with food allergies, keep in mind that there can be cross reactivity between chicken and turkey. Many dogs that are allergic to one will also react to the other. That said, dogs don’t read reports that tell them this, and one of my own dogs was so highly allergic to chicken that she ended up in the ER one night (why is it always at night or on weekends?), yet she ate turkey her entire life without any problems. So, it’s not a given that the dog will react, but if you’re trying to sort out which foods might be causing a problem, it’s probably best to keep this in mind. The same is true of fish in that there’s a common enzyme, so a reaction to one type of fish is usually an indicator that all fish should be avoided. And here again, my current dog shows that rules are meant to be broken because she tolerates cod and tilapia, but no other types of fish.
Where allergy is concerned, some things are carved in stone. The allergy to a food presented as kibble, canned, raw, or cooked is an example of this. Some things are iffy – like the cross reactivity between chicken and poultry being a problem for some dogs, and not others. And some things like a common enzyme in fish being problematic for a dog that doesn’t tolerate one variety, may or may not be an issue, but almost always is, so it’s something to keep in mind if you’re looking for novel foods.