Food Allergy in Dogs and Cats
Pet Food Allergies
To start, one of the things I ran into as a practicing veterinarian all the time was a wrong idea about what food allergies are. The common response when the possiblity of this being the problem was brought up was, "But he's eaten the same food all of his life."
Allergies are an over response of the immune system to something in the body or on the body (as in a contact allergy). The immune system gets a stronger response against whatever it protests the more it is exposed to it. Therefore, the most likely food allergy candidate is one who has "eaten the same food all his life".
The other misconception is that switching to a higher quality, more expensive food will handle the situation. Not true. Food allergies are to a specific particle such as a type of protein or grain. Chicken is chicken regardless of what company put it in the food or how much the food costs. If your pet has a chicken allergy, any food with it in the ingredients will create the trouble experienced.
So what can a food allergy look like? Pretty much anything. Common symptoms are recurring or constant skin or ear trouble, such as redness, itching, infections, "hot spots" etc...
Less commonly are digestive signs of vomiting, diarrhea and gas. I had one patient that vomited daily and was on a special digestive diet of chicken and rice; very bland diet. Food allergy was diagnosed, to guess what, chicken and rice. We changed the dog's food and she stopped vomiting immediatley.
I have seen one cat that had severe asthma like episodes until her food allergies were controlled by special diet.
It has also been reported that some behavioral problems may be related to this in pets (definitely is true in people.) I would certainly be ornery and maybe even aggressive if my skin always itched or I always had a stomach upset.
There may be other more obscure signs as well. Any recurring or constant disease sure leads to suspicion of an allergy of some sorts keeping it flared.
Also, food allergies tend to not be very responsive to treatment with antihistimines or cortisones. If an allergy is being treated with these but not responding well, it raised the question of "Is this food related?"
The diagnosis of food allergy can be a bit troublesome. There are blood tests, but they aren't completely accurate. The most common diagnostic test is a food trial on a very restricted diet. The pet is put on a food that has contents the pet has never eaten before. It takes a MINIMUM of 8 weeks to see if improvement will occur (except perhaps in the case of digestive signs being the symptom.). Once enough time has passed to see improvement, then one type of food at a time can be added to see if any reaction occurs. Honestly, most people just keep their pet on the special diet as it is easier and they usually are fine fed as a maintenance food.
Trouble can come up when the pet develops an allergy to the new food and then one has to start over again. In severe cases (diagnosed usually only by surgical removal of some of the tissue of the intestines and looking at the cells under a microscope in the case of digestive troubles.) medications to suppress the immune system must be used.
Fortunately, most will respond with a diet change if their owners are patient and strict enough about it.
I hope you find this data helpful.
Remember I am always glad to hear from you with experiences or data you may have or questions about this.
Dr. Jan