- Also called:
- Food hypersensitivity
- Food intolerance
- Adverse food reaction
What is food allergy?
Dogs and cats, similarly to humans, may have allergies to food. Some of these pets have symptoms that are limited to the skin, usually showing itching and irritation when they eat the food. They may also show soft stools, diarrhea, or other unusual symptoms.
Pets can become allergic to any component of their food. Since most pets eat commercial diets containing poultry, beef, dairy products, eggs, soy, and corn, these ingredients are implicated most often. But anything that the pet eats, from table scraps to treats, can cause an allergy. The development of the allergy is not contingent on the quality of the food that is fed, so the allergy is unlikely to resolve when the food is switched from one commercial product to another, even if the new food is of an exceptionally good quality.
Food-allergic pets account for a relatively small proportion of all cats and dogs with allergies, perhaps 5-15%. Yet, it is important to investigate this possiblilty, especially when the symptoms occur throughout the year.
How is food allergy diagnosed?
Unfortunately, neither blood testing nor intradermal testing is accurate in the diagnosis of food allergy. The only way to make a diagnosis, at this time, is to change your pet’s food to something completely “novel” for a period of 8-10 weeks. The “novel” food cannot contain the ingredients commonly found in pet foods and treats in even trace amounts. During this 8 week period, the food must be fed without the addition of table scraps, treats (including small amounts of cheese or hot dogs often used for giving medications), or chewable supplements. The only way to successfully perform a food trial is to be very strict with what the pet is allowed to eat.
The reason that the trial must be so long is that some pets will not show improvement until 4 to 6 weeks after stopping their original food. We may recommend either a commercially-prepared diet or a home-cooked diet for your pet. The advantage of the commercial diets is that they tend to be more palatable and easier for owners. Home cooked-diets, on the other hand, rule out the possibility that a stabilizer or preservative used in the production of the commercial food is causing the allergy. For this reason, if we strongly suspect a food allergy and cannot demonstrate it using a commercially prepared diet, we may then recommend a home-cooked diet instead.
If your pet’s symptoms improve at some time within the 8-week feeding trial, we may recommend further testing to confirm food allergy and to find out which ingredient is causing the allergy. Since we often prescribe other treatments during the food trial, it is important that we make sure your pet’s improvement is truly caused by the dietary change and not by the other medications, or a natural waning of the allergies. We do this by feeding your pet the “original” diet for a period of 1 to 2 weeks. Although it may take up to 6 weeks for symptoms of food allergy to abate, they will usually return much more rapidly. At this point, your pet’s food would be switched back to the trial diet to allow the symptoms to again disappear, and we may recommend further testing to find out exactly which ingredient caused your pet’s symptoms.
A word about ingredients
Specialty pet foods are expensive. They are often made with uncommon protein sources and with stricter quality control measures to ensure that one batch of food is not contaminated by another at the factory and that each batch is consistent. It is tempting to seek a less expensive “hypoallergenic” diet, and many are sold with this claim. Some may have similar major ingredients to ones that we have recommended. If you consider an alternative to a food that we have recommended, be sure to evaluate the ingredient list in fine print, not just what is advertised on the front of the bag! We have contracted with our distributor to provide home delivery of prescription foods to your door. Since we don’t carry any inventory, we pass on the savings to you. Remember, most diet trials don’t go on forever. And if you do find that your pet responds to the diet change, it will be worth the expense to see them comfortable again.