Managing Food Allergies in Pets

Food allergies are a hot topic in both the human and pet realms. These days, we all seem to be all hypervigilant about what type of food we put in our bodies. Naturally, I see many pet owners who desire to use the same diligence when it comes to making dietary choices for their pets. After all, we all want our pets to lead happy, healthy lives free of disease or other issues.
If you know (or suspect) that your pet is suffering from allergies to specific foods or ingredients, this article will help you get to the bottom of the problem.
How Common are Food Allergies in Dogs and Cats?
Contrary to popular belief, food allergies comprise only 10-20% of all allergic conditions in our dogs and cats, with the remaining 80-90% being of environmental origin. With so much focus on food allergies, I'm frequently faced with pet owners who swear that their cat or dog is allergic to something in their diet when often it isn't the case. That being said, it can be difficult, if not nearly impossible, to determine whether a pet has an allergy to food or to some environmental factor based on symptoms alone. For this reason, a diagnosis of food allergies should be considered in any dog or cat with the appropriate symptoms.
To What Types of Foods are Pets Allergic?
Pets can be allergic to many of the same types of food as people. Most often, the culprit is a protein (such as eggs and dairy products, fish, chicken, lamb or beef) or a carbohydrate source (such as corn, wheat, soy or rice). Some pets might be allergic to multiple food items. In addition, it is possible for pets to suffer from both food and environmental allergies.
What are the Symptoms of Food Allergies?
Most pets with food allergies experience itching and hair loss on the face, ears, forearms and/or thighs. Symptoms typically begin at a young age and do not  correlate with a change in seasons, as they do with environmental allergies. Occasionally, gastrointestinal signs such as vomiting and diarrhea might also be seen. Most cats and dogs with food allergies will also fail to respond to traditional allergy therapy. For some pets, symptoms might improve for a short time only to return or persist. Even cats and dogs without a prior history of food allergies might  develop symptoms in response to a new food, so be sure to mention any recent dietary changes to your veterinarian.
I Think My Pet Has a Food Allergy. What Should I Do?
If you suspect your dog or cat has an allergy to food, the best thing to do is to make an appointment to see your veterinarian as soon as possible. I see many owners who take matters into their own hands and make arbitrary diet changes without knowing the proper course of action. Doing so can often be a waste of time and money, and allergies can often worsen in the meantime, resulting in secondary infections and a heftier veterinary bill.
What Type of Allergy Testing Can a Veterinarian Provide?
During your pet's visit, your veterinarian will likely want to rule out other common causes of itching and hair loss such as mites or flea allergy hypersensitivity. If initial diagnostic tests rule out other issues, a food allergy should be considered. While blood testing for allergies is available, it is generally thought to be unreliable in cases of food allergies and is best reserved for pets who suffer from environmental allergies.
How are Food Allergies Treated?
The only way to know beyond a doubt whether your pet has a food allergy is to put him or her on a limited antigen diet (sometimes referred to as an elimination or novel antigen diet) trial, with the term "antigen" referring to any substance that stimulates an immune response in the body. The goal of the diet trial is to provide your pet with a completely new protein and carbohydrate source that he or she has never eaten before in hopes that symptoms will subside. Veterinary prescription diets are ideal for this purpose as they are specially formulated for pets with food allergies and contain obscure ingredients such as venison and sweet potato or duck and beet that aren't commonly seen in over-the-counter diets.
While waiting for the new diet to take effect, your veterinarian will likely prescribe medication to help alleviate your pet's symptoms. Antihistamines and steroids are commonly used to provide relief from itching. If present, secondary bacterial or yeast infections might need to be treated with topical or oral antibiotics or anti-fungal medication, depending on severity. Most pets with allergies of any kind can benefit from taking a regular omega-3 fatty acid supplement, which helps keep their skin and coat conditioned. Depending on your pet's particular symptoms, your veterinarian might also recommend medicated shampoo and conditioner or anti-itch sprays.
Though skin and gastrointestinal symptoms could improve in as early as four weeks, a limited antigen diet needs to be given for at least 12 weeks before it can be deemed ineffective. Not every pet will respond to every diet, so it might be necessary to try multiple prescription diets to find one that works for your cat or dog. It is very important for owners to be committed and to strictly adhere to feeding their pet the prescription diet during this time. This means no treats or table scraps, even if it's from a food source you suspect your pet is fine with. Anything additional that your pet consumes could interfere with the results of the diet trial. Once your pet is free of symptoms, foods can be added back into his or her diet one at a time to determine the cause of the allergy.
What if I Can't Afford a Prescription Diet?
It is true that prescription diets can be costly. However, in my experience, a pet owner will generally spend as much money, if not more in the long run, on repeat veterinary visits to treat allergic symptoms than on a limited antigen diet trial. If a veterinary prescription diet is simply not within your budget, talk to your veterinarian. He or she might be able to help you compare ingredients and find a commercial diet that will fit the bill. I generally caution against homemade diets, because it can be difficult for owners to come up with the proper balance of nutrients required—and it can also be very time-consuming to adhere to. However, some veterinarians do like them for pets with food allergies and, with a committed owner, they might work in some cases.
When shopping for "over-the-counter" food options you should be aware that just because a label claims a food is hypoallergenic does not qualify it for use as a limited antigen diet, nor does it necessarily indicate that it would be a good choice for a pet with food allergies. In fact, the term "hypoallergenic" is somewhat misleading. Pets can be allergic to a variety of different proteins and carbohydrates, so what is hypoallergenic for one pet might not be for another.
Should I Be Concerned about Food Additives?
While commonly implicated as a cause of allergic symptoms, food additives have not been demonstrated to play a large role in food allergies in dogs and cats. That being said, the goal of any good elimination diet trial is to limit the possible allergens your dog is being exposed to so, in my opinion, the shorter the list of ingredients, the better.
How will a Food Allergy Affect My Pet's Life?
Of course, since a food allergy cannot be cured per se, your pet will always need to avoid the food that has been identified as problematic. Common allergens such as chicken or beef are frequently used in treats and some flavored medications, so owners should always be aware of ingredients when giving their allergic pet anything outside of his or her diet. Some cats and dogs can develop new food allergies over time, but will generally respond favorably to a dietary adjustment. Pets with food allergies can live long and happy lives as long as they receive a proper diagnosis and are placed on an appropriate diet.

Dermatology for Animals, “Food Allergy,”, accessed on July 7, 2013.
Michael S. Hand, DVM, PhD, and Bruce J. Novotny, DVM. Pocket Companion to Small Animal Clinical Nutrition: 4th Edition. (Kansas: Mark Morris Institute, 2002), 330-332.
U.S. Food and Drug Administration, “Interpreting Pet Food Labels -- Part 2: Special Use Foods,”, accessed on July 7, 2013.