If you always experience a negative reaction after eating a certain food, you may assume that you have a food allergy. In fact, it’s more common to experience a food intolerance. Unlike true food allergies, which are caused by the immune system, there are many causes for food intolerance, such as lack of an enzyme needed to fully digest the food. If you think that you have a food intolerance, visit your doctor, who may order a blood test to determine whether you have a food intolerance.
Because food intolerances have several potential causes, diagnosing them can be difficult. Although there are blood tests available, some are not very accurate, particularly given the long list of potential foods involved in food intolerances. While most blood tests used to diagnose food intolerance are considered unreliable, there are blood tests that have been developed for specific forms of food intolerance, such as celiac disease. Blood tests may be used as an initial test for these food intolerances.
Blood tests for food intolerances, known as the IgE RAST test, are performed in the doctor’s office. It checks for antibodies that indicate your body is reacting to a certain food. Although it requires several vials of blood, blood tests can be helpful in that they enable the doctor to test several dozen potential trigger foods at the same time. Blood tests are chosen over other testing methods, such as a skin prick, when the patient has skin conditions such as eczema which may make the results of a skin prick test difficult to read.
Because blood tests may not always be accurate, diagnosis is made using the results of the test in combination with other factors, such as the symptoms experienced after eating the food. In addition to blood tests, your doctor may also ask you to keep a food journal, attempt an elimination diet to cut out potential trigger foods, breath tests, or an endoscopy.