Allergy Testing

Male: We are going to diagnose a kid with allergy, certainly we take a good history. How can you diagnose this correctly and know what the kid really is allergic to?

Dr. Marcus: You always start with a careful history trying to see when symptoms occur, what exposures trigger symptoms and what seasons trigger symptoms. Once you have this starting point, you have the general idea of the types of things that the patient is allergic to. The next step is to do allergy testing. To definitively identify the things that are causing the symptoms. There are two forms of allergy testing. Allergy blood tests and allergy skin tests and data shows us that allergy skin tests are more accurate than blood tests. Statistics say that allergy skin tests are 95% accurate in identifying things that the patient is allergic to. Whereas the blood tester only about 80% to a maximum of 90% accurate. Therefore, if tolerated, we always recommend using the allergy skin testing to be more definitive in identifying the allergy triggering the patient’s symptoms.

Male: So skin testing and blood testing could sometimes miss something that a good history could get.

Dr. Marcus: That is entirely true. No test is perfect and the data shows us that anywhere from five to 20% of allergies can be missed by the testing. That is why the history is always the most important starting point. If we see that exposure to certain things always triggers symptoms and regardless of what the testing shows, we should assume the child is allergic to that substance until proven otherwise. What we can do is eliminate exposure to that substance for a period of time, six to twelve months and then re-expose the patient to the substance another time to see if the symptoms return. This re-exposure or challenge would be the final step to proving that this substance is what is causing the allergy symptoms.



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