As Allergists, we commonly see patients who suspect they have an allergy to one or multiple foods. Sometimes the symptoms are striking and unmistakable, such as when hives and swelling develop within minutes of eating a particular food. At other times, the symptoms may be delayed and more vague, which clouds the causal relationship.
Often patients come bearing a blood test which shows one or multiple foods which were “positive.” Alternatively, the blood test is completely negative despite a seemingly clear allergic response to a food. Without the proper interpretation, these results may create confusion instead of clarity.
An important axiom in medicine is “treat the patient, not the test.” This means regardless of what the blood test or skin test demonstrates, the results must be correlated with the experience of the patient. The medical literature has shown that up to twenty percent of patients with a serious food allergy can test negative on a blood test. Conversely, food allergy tests are known to yield false positive results, both by blood and skin.
One of the Allergist’s tasks is to interpret the test results by comparing them to the patient’s history. When there is a match, a diagnosis can be established. In the case of a discrepancy, the ruling always favors the patient’s experience. For example, when a food seems to cause a reaction but both skin and blood tests are “negative,” further testing must be done before the food may be safely reinserted into the diet, as some food allergies may be life-threatening. Sometimes the reason for the mismatch is based on the definition of the word “allergy.” Patients often use the term to refer to any adverse symptom or reaction. Allergists use a much more narrow definition and test accordingly. An “intolerance” is not the same as an “allergy.”
For more information on this or any other allergy-related topic, contact Dr. Yoram Padeh, Dr. Zurik Waxenghiser or Dr. Michelle Eisenfeld at Asthma and Allergy Associates of Florida at 305-932-5662 or visit www.allergyweb.com.