Food hypersensitivity, food intolerance and other adverse reactions to food (ARF) cause a myriad of effects on several different
systems of the body, with the integument and digestive systems being most commonly affected. This two-part article series
provides insight into how ARF affects the skin in dogs and cats and how to definitely diagnose and manage patients with food
Most common culprits
Because food hypersensitivity can be the manifestation of a type I, III or IV hypersensitivity reaction, the onset of clinical
signs can range from minutes to days after ingestion of the offending allergen. In people, the allergen usually has a molecular
weight above 12,000 daltons, although this has not been confirmed in domestic animals, where the offending allergen may be
A number of studies published over the years have listed the most common food allergens in dogs and cats. Summarizing these
reports has led many dermatologists to conclude that animals have the potential to become allergic to any food stuff to which
they are exposed, especially proteins. In a 1996 report in dogs in the United States, the most common allergens were beef,
chicken, chicken egg, cow milk, wheat, soy and corn.1 In this report, 80 percent of the dogs reacted to just one or two items, although there are reports of dogs allergic to
as many as nine food items. Additional published reports list fish, rice and potato as foods known to cause adverse reactions.
The food items most commonly known to cause ARF in cats include chicken, fish and dairy products. A few minutes spent reading
the ingredient labels of most commercial cat foods will show these are the most common ingredients used in formulating the
One common misconception of clients and many veterinarians is that food allergy is more likely to develop only after a recent
diet change. In fact, when food allergies develop, the offending allergen has often been fed for more than two years, and
some patients will eat the same protein for many years before the allergy develops.
Further complicating the workup of a patient with a suspected food allergy is the recognition that some patients will have
cross reactions between related food ingredients. This phenomenon is well recognized in human medicine as well. Examples include
patients allergic to chicken who will not tolerate duck or turkey. Some patients allergic to beef will cross-react or show
clinical signs when exposed to other ruminants, such as lamb or venison. Fortunately, not all patients with food allergies
will have cross reactions, but some will.