Is it an allergy, intolerance or sensitivity?

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By Howard LeWine, M.D.
Posted on October 22, 2024

Q: My gut seems to be more sensitive to a variety of foods. Does this mean I have developed food allergies?

A: Many people confuse food sensitivity with a food allergy or food intolerance. While these conditions can have similar symptoms, they are quite different.

Food allergy: A food allergy happens when the body mistakes a food ingredient as harmful and defends itself by turning on your immune system, such as producing high levels of a type of antibody called immunoglobulin E. Sometimes a food allergy is life-threatening and requires immediate medical attention.

Common food allergies include immune reactions 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 can also experience hives, throat swelling and shortness of breath.

Food intolerance: A food intolerance usually means you lack or have an insufficient amount of one or more enzymes needed to break down certain ingredients.

For example, 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.

Food sensitivity: This is an individual’s adverse physical response to a certain food, beverage or ingredient. The symptoms might be only 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, which is caused by an immune reaction to gluten that requires complete avoidance of the protein.

A good 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.

Elimination diets are trial-and-error, and you may have to try different foods and amounts until you find the right combination. While it’s possible to follow an elimination diet on your own, consider requesting consultation with a nutritionist or dietitian.

These professionals can guide you through the process and help you track your progress, as well as offer support tools like creating a food diary and symptom chart.

A dietitian or nutritionist also can make sure you don’t cut out foods that provide necessary vitamins and nutrients.

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, see health.harvard.edu.