Itchy Skin. . . but No Fleas??
Food allergy is also referred to as dietary allergy/hypersensitivity, food intolerance and most recently, cutaneous adverse food reactions (CAFR). Food “allergy” implies an immune system- mediated process, in comparison to “food intolerance” which is simply an abnormal response to ingested food. A true food allergy is the third most common cause of skin allergies in the dog, second to flea allergic and atopic (inhaled allergen, ie. seasonal) dermatitis. Up to 50% of the time pets have food allergy in combination with another type of allergy.
Food allergies are caused by a sensitivity to a particular component of diet (major or minor) such as beef, chicken, eggs, dairy, fish, lamb, corn, soy, wheat, food dye, preservative or stabilizer. The most common are beef, chicken, corn, wheat, cow’s milk, soy, eggs and fish.
The most common clinical sign is non-seasonal itching. This can be accompanied by hair loss, reddened skin, chewing, biting, scooting, ear or skin infections, and it may be mild or extremely severe. Secondary bacterial or yeast infections typically worsen the itching and complicate diagnosis.
80% of dogs have an ear infection as one of the symptoms of food allergy; in fact 25% of dogs have an ear infection as the ONLY symptom. The other common regions of the body that are infected include the face, armpit and groin regions, abdomen and paws. Other signs can include dry, flaky skin, recurrent bacterial skin infections, hives or even vasculitis. 10-15% of patients also have intermittent vomiting, diarrhea, increased number of bowel movements and gas.
Diagnosis is made by performing a food trial, which means feeding your pet a type of food that they have never had or only had infrequently. The only accurate diagnosis is based on a strict elimination diet that results in elimination or reduction of the itching. It’s not the same just to switch brands since most brands share similar proteins, preservatives and starches. And, you may not see improvement for 4 weeks!
For 10 weeks (longer in cats!) no other table foods, pet foods, vitamins, treats, rawhides, flavored toothpaste can be given. Selecting an “appropriate” elimination diet can be tricky. Home-cooked diets are considered the gold standard, but can be difficult and time-consuming for owners. The ideal diet should consist of a novel protein and carbohydrate source that the dog or cat has not eaten before. Examples of novel protein sources include: pinto beans, venison, rabbit, ostrich, alligator, kangaroo and duck. Packaged diets are available and can be a more convenient alternative to home-cooked diets.
Hydrolyzed protein diets are also a possibility (ie Hill’s z/d). These diets are beneficial in humans with food allergies, and are based on feeding small protein fragments that are more easily digestible.
The key to successfully diagnosing and treating food allergy in pets is to discontinue all foods other than the prescribed diet. Treats can consist of pieces of kibble or balls of canned food. Cookie “treats” can be made by placing balls of moistened or canned diet on a cookie sheet and baking at 400 degrees for one hour.
After the food trial is complete, you can either challenge the dog or cat with previous diet or continue to feed the elimination diet long-term, provided it is complete and balanced. The prognosis for these pets is good provided that the offending food product can be removed permanently from the diet.