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Ask the Allergist

Could medicine use affect my allergy test results?

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I was diagnosed with allergy-induced asthma about 5 years ago. I recently had a blood test for allergies. The results were negative. I've been taking antihistamines for a year or so. Is it possible my use of those antihistamines affected the results?

There are two ways to test for allergic sensitivity to aeroallergens. One is skin testing. Another is a serum-specific IgE blood test. Both can be done by a board-certified allergist. These tests often match but not always. The use of antihistamines can block the skin tests but would not block the blood tests. If it's possible that you have allergic asthma, you may want to discuss your symptoms with an allergist. You may also want to consider skin testing.

Allergy, Treatment
Answered by

Douglas T. Johnston, DO, FAAAAI, FACAAI, is an allergist/clinical immunologist at Carolina Asthma & Allergy Center in Charlotte, North Carolina, and Assistant Professor at Edward Via School of Osteopathic Medicine in Spartanburg, South Carolina. He is a fellow of the American College of Allergy, Asthma, and Immunology (ACAAI) and the American Academy of Allergy, Asthma, and Immunology (AAAAI). He has lectured at national and international medical conferences and has publications in several medical journals, including “Clinical Immunology,” “World Allergy Organization Journal,” “Journal of Allergy, Asthma, and Immunology,” “The Journal of the American Medical Association,” and the “New England Journal of Medicine.”

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I've had things I knew I was allergic come up negative on blood tests but positive on skin prick tests and obviously positive when exposed to the allergen. From what I understand there is a difference in allergic responses that isn't always picked up on blood tests, and also that sometimes an allergen has more allergenic components in it than what is looked for on a specific ige blood test but that do often pick up on the skin prick test. I have also heard some allergic reactions are more delayed and others more immediate so it us good to different tests to pick up those results. So ultimately (as a non medical person but with experience with different testing) I would say talk to your doctor about trying a skin prick test as give them any info on reactions you have had in the past on both tests and in real life experience.

Last edited by Shea
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