Around 12 million people in the U.S. have food allergies. Reactions occur about an hour food after the food is eaten. Symptoms are rash, hives, hitching, swelling, trouble breathing, nausea, vomiting, or diarrhea. Common food allergies include: eggs, fish and shellfish, milk, peanuts, and wheat. A food allergy is more severe than a food intolerance. With an allergy, even a trace of the food can start a reaction in the body. Be sure to read food labels when grocery shopping and ask about ingredients at restaurants.