Q: I've been having digestive issues and problems losing weight, despite maintaining a healthy diet and exercise problem.  I read about how food allergies could cause this? Is this possible and how would I find out?

Food allergy affects approximately 12 million people in the United States, and may be on the rise, particularly in children.  The most common foods associated with food allergy are what allergists refer to as "the big eight":  milk, egg, wheat, soy, peanuts, tree nuts, fish, and shellfish. 

The typical reactions that occur with food allergy may include hives or itchy skin rash, angioedema or skin swelling, and gastrointestinal symptoms such as vomiting, diarrhea, or abdominal cramping.  In more severe cases, it is possible to have a life-threatening allergic reaction called anaphylaxis, which may include throat tightness, wheezing, chest tightness, difficulty breathing, low blood pressure, or worst case scenario, death.  Most people are keenly aware of allergic reactions to foods because of the potentially dramatic symptoms involved.  Food allergies, especially in children, can sometimes lead to inability to gain weight or failure to thrive, particularly if the reaction to the food consists of diarrhea. 

There is a difference between food allergy and food intolerance, which can sometimes be associated with digestive issues.  Food intolerance does not have the same immune mechanism as food allergy, and therefore is not usually life-threatening.  Food intolerance can vary in symptoms such as inability to properly digest milk due to lactose intolerance, to more vague symptoms such as headaches, bloating, weight gain, and irritability. 

While food allergy generally occurs fairly quickly after eating the offending food, food intolerance symptoms may show up much later.   It is important to see an allergy specialist to determine whether your symptoms might be caused by true food allergy or whether you might have food intolerance.  Simple allergy skin testing or blood testing may help to clarify your digestive issues. There are immune-mediated disorders such as Celiac disease which are associated with gluten-intolerance (found in wheat products) and may cause digestive issues as well. 

True food allergy does not cause weight gain, as people are usually unable to eat the foods because of the symptoms mentioned above.  If you are having difficulty losing weight despite maintaining a healthy diet and exercise regimen, it would be important to explore this with your physician, as there may be other reasons (sometimes hormonal) which could be the cause.  Both food allergies and food intolerances can be managed effectively to allow you to maintain a healthy diet, healthy weight, and best of all, feel well. 

Dr. Princess Ogbogu is a pulmonologist and allergist at the Lung Center of Ohio State