In addition to food allergies and intolerances, people can also have reactions -- such as headaches, allergylike symptoms, and nausea -- to food additives, preservatives, or naturally occurring compounds in certain foods.
"These sensitivities are becoming more common as we eat more processed foods," says Stephen M. Dandalides, M.D., a spokesperson for the American College of Gastroenterology and an assistant clinical professor at Eastern Virginia Medical School in Norfolk.
Here are three of the biggest offenders.
Intolerance to the flavor-enhancer monosodium glutamate (MSG) can cause headaches, nausea, sweating, flushing, and chest discomfort. MSG is found in Chinese food and soy sauce, as well as in canned soup, bouillon cubes, salad dressing, barbecue sauce, frozen entrees, and many fast foods.
These can occur naturally in the production of wine and beer -- but are also added to preserve foods and prevent mold growth. They give off sulfur dioxide, a gas that can cause wheezing, chest-tightening -- and can result in dangerous constriction of the airways for people with severe asthma.
Found in certain fermented foods (some cheeses and wines) and fish (such as tuna and mackerel), these can cause allergylike symptoms: headache, flushing, rapid heart rate, and wheezing.