Food sensitivity much more common than food allergy

Q: I recently developed abdominal discomfort and bloating after eating certain foods that didn’t bother me before. Does that mean I am developing food allergies?

A: People often confuse a food sensitivity with a food intolerance or allergy. While these conditions may share some symptoms, they are quite different.

Food sensitivity is an individual’s adverse physical response to a certain food, beverage or ingredient. The symptoms are usually similar to what you describe: digestive problems, such as abdominal pain, bloating and gas.

However, you may also have fatigue, headache or “brain fog.” For example, some people have digestive problems and other symptoms after eating too much gluten, a protein found in wheat, barley and rye. This is different from celiac disease, caused by an immune reaction to gluten that requires complete avoidance of the protein.

Food intolerance refers to a lack of the enzymes needed to break down and absorb certain ingredients. The inability to digest lactose, the sugar in dairy products, is a common food intolerance. When lactose is not absorbed, it ferments in the colon and leads to symptoms like gas, bloating, nausea and intestinal pain.

A true food allergy can be a serious problem. It occurs when the body mistakes a food ingredient as harmful and defends itself by producing high levels of a type of antibody called immunoglobulin E. Sometimes a food allergy is life-threatening and requires immediate medical attention. The most common food allergies are to shellfish, nuts, fish, and eggs. A person with a food allergy may have symptoms similar to an intolerance or sensitivity, but he or she also can experience hives, throat swelling, and shortness of breath.

Of the three, food sensitivity is the most common as we age. The first step is to identify the problem foods. You may have a good idea which foods are the troublemakers, but your sensitivity also could be caused by combinations of foods or even certain amounts.

The best approach to manage food sensitivity is to adopt a short-term elimination diet. It works like this: You eliminate a particular food for about two to four weeks to see if your symptoms recede. Then you reintroduce the food gradually, according to your tolerance, to see if your symptoms reappear.

Once you’ve identified the problem food (or foods), you are guided on whether to adjust portions, change your eating habits — like when, and how fast, you eat — or switch out the food entirely.

(Howard LeWine, M.D., is an internist at Brigham and Women’s Hospital in Boston and assistant professor at Harvard Medical School. For additional consumer health information, please visit www.health.harvard.edu.)