Food allergy is one of the most misunderstood allergic reactions in dogs. It is unfortunately further complicated by marketing and many unsubstantiated claims in the marketplace. In reality, food allergy is a fairly simple concept. Dogs and cats with food allergy have developed a hypersensitivity or allergic reaction to one or more of the ingredients they have eaten in the past, or are currently eating. If the offending protein(s) or carbohydrate(s) can be removed from the pet's diet, then progress should be seen, over a period of 6 to 8 or sometimes 12 weeks.
Since there is no reliable blood test or skin test for food allergy, the specific diagnosis relies on a properly performed elimination diet trial. An elimination diet trial is the complete elimination of all ingredients that an animal has eaten before since many of them could be a cause of food allergy. This must include the elimination of all treats, chews, bones, flavored heartworm or flea prevention since any of these may trigger an allergic response.
Food allergy in dogs and cats can also be complicated by secondary infections, such as bacterial or yeast infections. This can make the diagnosis more challenging since these infections can be itchy on their own and may prevent progress from being seen even when an elimination diet trial is properly performed.
The choice of diets used to perform an elimination diet trial is critical since all previously fed ingredients must be avoided. In addition, veterinarians and pet owners must also be sure to avoid ingredients that may cross react or diets with cross contamination of ingredients. Cross reaction occurs when two ingredients are similar enough in structure that allergy to one of them also results in reaction to the other. Examples of documented cross reaction include those seen with duck and chicken. Cross contamination is the contamination of a particular diet with ingredients that are not listed on the label. Multiple studies have shown this to be a problem with many over-the-counter dog foods.
While it is tempting for a pet owner to perform multiple diet changes to try to identify food allergy, it is preferable to do this only after consulting with a veterinarian or veterinary dermatologist in order to have a comprehensive approach that is most likely to have success.
Food allergy symptoms in dogs and cats are most commonly associated with itchiness. This may include licking, scratching, chewing and rubbing at a variety of areas including the face, ears, rear (including scooting), armpits and others. The challenge is that food allergy symptoms are clinically indistinguishable from those of environmental allergy. Some food allergic pets may also develop gastrointestinal symptoms including soft stools, diarrhea, frequent bowel movements and even vomiting.
The only reliable method for food allergy in dogs and cats is a strict elimination diet trial. While there are a number of blood tests, and even tests on hair and saliva that claim to test for food reactions, none of these have been shown to provide reliable, repeatable or useful information regarding food allergy. As a result, the only reliable method is to remove all ingredients to which a pet has been previously exposed (i.e has eaten before) since any of them could contribute to food allergy symptoms. This must be done strictly with no treats, chews, rawhides, or flavored medications since any of these may also cause reactions.
Food allergy can develop to any ingredient an animal has eaten before. It is therefore impossible to list the most common food allergy for every pet. Commonly documented food allergies for dogs may include chicken, beef, fish and proteins, but also occasionally carbohydrates like rice and corn. It is important to recognize that every pet is different and the diagnosis of food allergy via strict elimination diet trial should be tailored to the individual pet with their personalized dietary history considered.
Food allergies CAN be self-diagnosed by a diligent pet owner if the right approach is used and if there are no additional complicating factors. Since there are no reliable blood or skin tests to diagnose food allergy, a strict elimination diet trial must be performed. To perform this trial, a pet owner must remove all ingredients to which a pet has been previously exposed (i.e. has eaten before) since any of them could contribute to food allergy symptoms. If the pet improves over an 8 week period, foods are re-introduced in order to document which of them cause a reaction. If problems do NOT improve, the pet may not be food allergic, or there may be additional complications such as bacterial or yeast infections that prevent the expected progress. If you suspect that your pet has food allergies see your veterinarian or a veterinary dermatologist to help with the right approach.
Food allergy is an common cause of itching, scratching, skin and ear disease in dogs and cats. If you suspect food reactions in your pet, it is ideal to consult your veterinarian or a veterinary dermatologist, since there are a wide variety of causes of these symptoms including both food and environmental allergies. If your veterinarian feels food allergy is a possibility, he or she may suggest a strict elimination diet trial. Since there is no reliable skin or blood test for food allergy, a dietary plan must be devised to avoid all ingredients that your pet may have eaten in the past.
The only reliable test for food intolerance or food allergy is a strict elimination diet trial. While there are blood, hair and saliva tests available, none have been shown to be proven reliable sources of information for diagnosis of food allergy in pets. The only reliable test for food reactions is to remove all ingredients to which a pet has been previously exposed (i.e. has eaten before) since any of them could contribute to food allergy symptoms. If the pet improves over an 8 week period, foods are re-introduced in order to document which of them cause a reaction.
Food intolerance or dietary intolerance is considered a slightly different category of food reaction that may not require previous exposure. Symptoms of food intolerance are often gastrointestinal (diarrhea, vomiting etc.). Elimination and rechallenge are still the only trusted method to document exact causes of food intolerance.
Food allergy is a true allergic reaction in which the immune system begins to develop a hypersensitivity to one or more ingredients that an individual has eaten before. Food allergy requires that a pet has been exposed to the offending allergen or a similar ingredient to which there is cross reaction. Food intolerance is instead a reaction that requires no prior sensitization and may occur on the first exposure. In dogs and cats food intolerance reactions are more often gastrointestinal and include diarrhea or vomiting.
Food allergies may appear in dogs and cats at almost any age. Studies show, however that food allergy is more likely than environmental allergy to appear in very young animals (less than 6 months) and in older animals.
ANY food ingredient can cause food allergy in pets. Offending allergens are most often a protein or a carbohydrate. Which ingredient(s) cause reactions in an individual depends on what that pet has eaten before. Since food allergy requires previous exposure to an ingredient, this can vary significantly from one pet to another.
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