Evaluating Food Allergies

Food allergy or food intolerance affects nearly everyone at some point.  When someone has an unpleasant reaction to something they ate, they often think that they have an allergy to the food.  Food allergy is an abnormal response to food that is triggered by a specific reaction in the immune system and expressed by certain symptoms.  Food intolerance is also an abnormal response to food.  Its symptoms can resemble those of food allergies however food intolerance is fare more prevalent and is triggered by several different mechanisms that are distinct from the immunological reaction responsible for food allergy.  Anyone with a food allergy must attempt to identify and prevent them because these reactions may cause devastating illness and potentially be fatal.

Diagnosing a food allergy can be a challenge for most doctors.  First the doctor must determine if the patient is having an adverse reaction to specific foods.  The doctor makes this assessment with the help of a detailed history from the patient, the patient’s dietary diary, or an elimination diet.  The doctor then confirms the diagnosis by the more objective skin tests, blood tests, or food challenges.  The dietary history is the most important diagnostic tool. The physician interviews the patient to determine if the facts are consistent with a food allergy.  If the patient’s history, dietary diary, or elimination diet suggests that a specific food allergy is likely, the doctor will then use tests, such as skin tests, blood tests, and a food challenge, which can more objectively confirm an allergic response to food. 

Some people have an allergic reaction to a food that is triggered by exercise.  As the body is stimulated by exercise, a person with an exercise induced food allergy may feel itchy and lightheaded.  In more severe cases, reactions such as hives or anaphylaxis may occur.  Not eating for a few hours prior to exercising may help prevent this problem.  Some fresh fruits and vegetables may also trigger a mild allergic reaction that causes the mouth to tingle or itch.  This is called cross-reactivity in which the proteins in fruits and vegetables cause the reaction because they are similar to allergy causing proteins found in certain pollens.  Most cooked fruits and vegetables generally do not cause cross-reactive oral allergy symptoms.

Food allergy reactions can vary from person to person.  Some reactions can be very mild and only involve one part of the body.  Other reactions may be more severe and involve more than one part of the body.  Reactions can occur within a few minutes or up to a few hours after contact with the food.  A serious allergic reaction with widespread effects on the body is known as anaphylaxis.  This sudden and potentially life threatening allergic reaction involves two or more body areas.  In addition, there may also be swelling of the airway, serious difficulty with breathing, a drop in blood pressure, loss of consciousness, and in some cases, even death.  The primary caregiver will look for any other condition that could cause the symptoms.  If the doctor suspects a food allergy, the patient will likely be referred to an allergy specialist, who will ask in depth questions, perform a physical exam, and perform tests to help make a diagnosis.