The Important Difference Between Clinical Allergy and Allergy Sensitization

A doctor's review of patients' medical history is as important as skin test results in diagnosing clinical allergies.

A doctor’s review of patients’ medical history is as important as skin test results in diagnosing clinical allergies.

I’m sure you have patients come into your office and say: “I was once tested by an allergist and told I was allergic to everything green!” I’m  always dismayed when I hear that patients were given results in this manner. Almost no one is allergic to “everything green.” Patients may be sensitized to multiple allergens but most likely they’re not allergic to them all. Making the distinction between clinical allergy and allergy sensitization requires the doctor to study each patient’s health history in conjunction with allergy test results.

Let’s demonstrate with a food allergy example… A patient visited my office and told me that he attended a party and ate a piece of cake. Within 15 minutes, he developed hives (urticarial) all over his body. He wasn’t sure what was in the cake but was worried about what he should avoid in the future. I tested him and the results showed a positive for tree nuts — walnuts, cashews and pistachios. The skin tests also showed positive for milk and eggs, but he told me that he eats eggs and drinks milk all the time without a problem. We found out that the cake contained walnuts, so I diagnosed him with walnut and tree nut allergy. I explained that his positive allergy tests to egg and milk demonstrated that he has allergic sensitization to the raw pure proteins in those foods, but, with no clinical complaints, he can still continue to eat them.

Here is another example of a potentially confusing situation that you may encounter using the AllerVision skin testing panels: you test a patient and find she is allergic to several tree pollens, grass pollens and ragweed pollen. The patient’s history says she only has symptoms in the spring — from March until June. She has no symptoms in the fall. My assessment would be that she has clinical allergy to the spring pollens, trees and grasses, and allergic sensitization to ragweed. This distinction becomes important not just in educating the patient, but in determining the patient’s course of immunotherapy. In this case, you might decide to treat the patient for the trees and grasses but leave the weeds out of the equation.

The allergy world is buzzing with research on diagnostic techniques to delineate clinical allergies more clearly. One company is working on a blood test that involves Resolve Component Testing. That measures a protein called Ara h2 — highly specific for peanut allergy. Preliminary studies indicate 95% accuracy. In the meantime, don’t forget the importance of clinical history in conducting the “detective work” required to distinguish clinical allergy from allergy sensitization. And remember that, as always, the AllerVision clinical team is available to work with you and discuss your cases any time you have questions.

Dr. Dean Mitchell

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