WebMD reveals the signs, symptoms, and triggers for food allergies in dogs.
By Sandy Eckstein
WebMD Pet Health Feature
Reviewed by Audrey Cook, BVM&S
Your dog is itching like crazy and shaking his head constantly. Your vet just told you it could be a food allergy. What does that mean? To find out, we talked to Susan Wynn, an internationally known expert on holistic pet care. Wynn is former president of the American Holistic Veterinary Medical Association, a clinical resident in nutrition at the University of Tennessee College of Veterinary Medicine and author of four textbooks on integrative practice, focusing on dietary supplements such as nutraceuticals and herbs.
Q: How common are food allergies in dogs?
A: Ten percent of all allergy cases in dogs are food allergies. Dogs also can suffer from food intolerance, which is different from a food allergy.
Q: What are the signs of a food allergy?
A: Anything from chronic ear inflammation, gastrointestinal problems, and chronic diarrhea to chronic gas, licking their feet, or an itchy rear end. More uncommon, and probably not agreed upon, symptoms might include seizures, asthma, and chronic sinusitis/rhinitis.
Q: What are the most common things that could trigger a food allergy in my dog?
A: It's a genetic problem, and when it's triggered, it's by exposure to whatever they're allergic to. The most common allergens are beef, dairy, wheat, egg, chicken, lamb, soy, pork, rabbit, and fish. And, most dogs are usually allergic to more than one thing.
Q: What causes these allergies?
A: It's a multi-factorial thing, but certainly you have to have a genetic predisposition to develop allergies. The environment can affect it, too.
There's a lot of research going on right now to determine what, in early puppyhood or early kittenhood, makes the immune system more likely to express that trait. There's an immune education process happening in the first few weeks of life. Young animals treated with antibiotics could potentially be predisposed to problems later in life because antibiotics change the environment inside the gut, which is the largest immune organ in the body. That could be a predisposing cause, but then the trigger would be being exposed to the allergen.
Q: Are some breeds more prone to food allergies?
A: There are some, but I think it depends on whom you talk to. It also can vary by country or part of the country. It may be as simple as what breeders, with their line-bred family of animals, are in your area. So if you have a very prominent breeder who is breeding a line known for their allergies, you're going to think that breed commonly has food allergies. In my experience, retrievers, German shepherds. Dachshunds, cocker spaniels, and rex cats are the most commonly affected breeds.
Q: How do I determine if my dog has food allergies, or something else is causing the problem?
A: There's only one way to diagnose food allergies accurately, and that is an elimination diet and challenge. So what we do is take the dog off all the foods it's eating and we put him on a food that he's never had before. With all the exotic diets out there now, this can be pretty difficult. I've sent people out for alligator and yak. Once the dog has improved, we start reintroducing the old foods that we think caused the problems in the first place. If he has a reaction, which usually takes a few days to a few weeks, then we know he has a food allergy.
There's specific testing to rule out other problems as well. For instance, you might take a sample of discharge from the ears to see if there's a problem there, or do skin testing for environmental allergies. Blood testing is not an accurate test for any allergy.
Q: Will changing my dog's diet trigger a food allergy?
A: If the dog has been sensitized to something in that diet it could. There's no way of knowing if your dog has been sensitized to an ingredient, though.
Q: Can my dog suddenly develop a food allergy to something that he's eaten for years with no problems? Will this keep happening?
A: That's common in food-allergic dogs. They have to be sensitized; they have to have been exposed for some period of time. So, in general, they're not going to react really dramatically the first time they eat it but a dog that has eaten a food for years could suddenly become allergic to that food.
If an elimination diet improves the pet's clinical signs and the owner is able to find two to three diets the dog can tolerate, I recommend rotating through them every two to three months. The whole point is to keep them stable for a period of months to years so you can eventually do their challenge testing to identify what the dog is really allergic to. If you're really lucky, then you can go back to a more normal diet and not these expensive, exotic diets.
And if they're young enough, food allergies sometimes do resolve themselves.
Q: How do I treat a dog with food allergies?
A: You can try to cover up the signs, but if you've got a disease that's caused by what you put in your mouth every day, the best treatment is to stop putting that in your mouth every day. I use herbs all the time, and I do think they can help, but not as much as avoiding what's causing the problem.
Q: Should I cook for my dog, rather than buy her food? What about a raw diet, will that help?
A: The upside of a cooked diet is you know exactly what's going in it and you can control that. The disadvantage is it's more trouble and, unfortunately, most people won't do it right. They will leave off supplements, they won't follow instructions, and they'll end up giving their dog or cat an unbalanced diet.
There's nothing magical about raw diets. Some dogs do very well on them and some dogs do not do very well on them. The protein structure might be different from that in a cooked or processed diet and that does make a difference for some dogs. But it's not common enough that we need to tell everybody they should try a raw diet.
Q: Is there anything I can do to keep my puppy from developing food allergies?
A: I don't think anyone is going to tell you that you can prevent food allergies if your puppy is predisposed. My opinion is that if you provide a diet that has some variety in it, so they're getting a natural rotation, you're maintaining gut health by doing that.
I do recommend for young puppies and kittens that people put them on probiotics. I'm very concerned about the use of antibiotics in growing animals. I think it messes up their gut balance and I think it may make them more likely to become allergic over time. So for puppies, I try to avoid antibiotics and use probiotics up to six months to one year of age and give them a diet that's fairly high in variety.