It isn't always easy to avoid foods that trigger allergic or intolerance reactions. Offenders may show up where you don't expect them. Milk, soy, wheat, nuts, and eggs are staples of the food industry. It's got soy, milk, and whey. Restaurant foods are even trickier because chefs and waiters may not know what ingredients were added to the broths, sauces, breadings, and other prepared foods they cook with.
Trace amounts can trigger a reaction.
People who are exquisitely sensitive to certain foods report that just being in the same room as the food can trigger an allergic reaction. Clearly, it doesn't take much. Foods can be contaminated with allergens. In a disturbing new unpublished FDA study, inspectors found that only half of 85 randomly selected candy, ice cream, and baked-goods plants in Minnesota and Wisconsin were checking to see that the ingredients listed on their labels matched the ingredients in their foods. Many used the same utensils to make foods with peanuts or eggs and foods that were supposed to be allergen-free.