MANHATTAN, Kan. – Nancy Knickerbocker was 18 years old before she found out she had what appeared to be a food allergy.

Some years ago, on her high school senior trip, the retired Neodesha High School teacher remembers eating shrimp for the first time.

Hours later, "I just blew up," she says, recalling the swelling in her hands, face and body.

"Living on the farm (near Mapleton, Kan.)," Knickerbocker said, "we didn’t have shrimp every day."

According to Kansas State University associate professor of human nutrition Barbara Lohse Knous, shrimp and other crustaceans are among the most common food allergens. The others include fish, cow’s milk, eggs, soy-based foods, wheat, peanuts and tree nuts (such as walnuts).

That’s especially good information during the holidays, when many of those foods are included in recipes and foods served at parties and other get-togethers, says Lohse Knous, a human nutrition specialist with K-State Research and Extension.

"Usually, persons with food allergies are told to be good label readers to detect problem food items," Lohse Knous said. "However, foods served in restaurants and at parties are never labeled and might be made from recipes that are changed according to available ingredients."

A food allergy is an adverse reaction to a food or food component that involves the body's immune system. Allergic reactions to food are rare, but can be caused by any food.

Another, more common class of food sensitivities is a food intolerance, a reaction to foods or ingredients that do not involve the body's immune system (an example is lactose intolerance). Intolerance reactions are generally localized, short-lived and rarely life threatening.

In fact, Lohse Knous says Knickerbocker’s reaction more likely was a food intolerance, since Knickerbocker now can eat shrimp without the reaction she experienced years ago.

Still, the National Institutes of Health reports that approximately 5 million Americans (including 4-8 percent of children and 1-2 percent of adults) have a true food allergy.

According to the International Food Information Council, the body's immune system recognizes an allergen in a food as foreign and produces antibodies to halt the "invasion." As the battle rages, symptoms appear throughout the body. The most common reaction sites are the mouth (swelling of the lips), digestive tract (stomach cramps, vomiting, diarrhea), skin (hives, rashes or eczema) and the airways (wheezing or breathing problems).

"The only way to prevent food allergy reactions is to avoid the food; allergy shots aren’t recommended for food allergies because they may pose a serious risk and cause breathing problems," Lohse Knous said.

To help holiday guests avoid allergic reactions to food, Lohse Knous has these tips for party hosts:

* If possible, ask guests about possible allergies. "People will think this is thoughtful, not snoopy," she said.

* If the guest list is long, and it’s difficult to know if guests have food allergies, reconsider menu items that may include common allergy foods;

* If a recipe calls for a highly allergenic food, consider a substitution. For example, raisins or dates can replace chopped nuts.

* Put place cards or labels by foods to show the ingredients, especially if the recipe includes highly allergenic foods.

For more information on healthy eating and food safety, interested persons may contact their local Extension office.