We've recently been covering allergies in cats and dogs: The top two are atopy (inhalant allergies to airborne pollens) and flea-allergy dermatitis.

The third most common allergy is to food — generally, symptoms include a non-seasonal itchiness, particularly of the face, feet, armpit, groin and ears.

Food allergy is a condition where the body's immune system reacts adversely to an ingredient in food. Some of the most common offending agents include beef, chicken, turkey, milk, eggs, corn, wheat and soy.

Some of the breeds most often affected are miniature schnauzers, cocker spaniels, Labrador retrievers, golden retrievers, wheaten terriers, bichon frises, German shepherds and sharpeis.

In addition to skin reactions, which include itchiness, hair loss and scabs from scratching, you can also see gastrointestinal upset (diarrhea and flatulence), respiratory problems (sneezing) and possible seizures. Pets with food allergies are more likely to have other types of allergies as well.

Diagnosing food allergies can be difficult, as no inexpensive, reliable test exists.

Also, owners might have trouble believing that a skin problem can be food-related because the pet has been on the same food — possibly a premium food, or even lamb-based — for years, without problems.

Unfortunately, lamb- and rice-based diets are not necessarily less likely to cause allergies than any other diet. Here's why: For many years, lamb was hardly ever fed to pets in the U.S., so it was used as a novel protein source for pets placed on "elimination" diets (one that eliminates one food item at a time, to determine the source of a food allergy).

As more and more dog-food brands started using lamb, however, its usefulness as a novel protein source decreased. So don't believe the hype; a commercial diet that includes lamb will probably not be hypoallergenic for your pet. You need to investigate the protein source in your pet's usual food and use a protein and carbohydrate source that your pet has not been exposed to.

Your pet then needs to be on this food, and only this food, for four to eight weeks. This means no table scraps, no flavored vitamins, no flavored heartworm pills. If this diet is not used exclusively, it will not be a meaningful test.

This, of course, takes total commitment from every family member — no cheating, or the test is void. See your vet to help you design a hypoallergenic trial diet. Remember: Commitment is the key.