BY ROGER SMITH

Q: I've heard that I shouldn't feed my pets a food that has corn in it because most pets are allergic to it. Is this true, and what signs would my pets show if they were allergic to corn?

A: Although corn seems to have a bad reputation with some pet food retailers, it isn't one of the more common ingredients known to cause food allergy in pets. The most common food offenders are, in order, beef, dairy products, chicken, lamb, fish and eggs. Wheat, corn and soy can cause food allergy, but are less commonly involved.

Pets can have two basic problems with a specific diet. Food intolerance is a gastrointestinal reaction to a specific type of food with the main symptoms being vomiting and/or diarrhea. Food allergy is a true allergic reaction to an ingredient in the diet. Symptoms include mild to intense itching and skin lesions involving primarily the face, ears, feet, legs, armpit and tail/anal areas. Signs of food allergy can easily be confused with other skin problems, including sarcoptic mange, bacterial or yeast infections and other allergies such as flea bite allergy and inhalant allergy (called atopy or atopic dermatitis). One should be suspicious of food allergy if the symptoms continue year-round (aren't seasonal), aren't very responsive to antibiotic or steroid treatments, and have the typical distribution pattern of skin lesions.

The only way to diagnose food allergy is to feed a diet free of the offending ingredient. Common diets recommended are those made with novel protein/carbohydrate combinations (meaning those to which the pet has never been exposed). Frequently used foods might include duck and green pea, venison and potato or even kangaroo as main ingredients. Prescription diets containing hydrolyzed proteins (to make them less allergenic) are also available. These diets must be fed for 8-12 weeks with no treats, rawhides, flavored medications or other food items. If skin symptoms resolve during this time, food allergy is the likely diagnosis.