Quick question. Can I do blood allergy testing while on antihistamine?

Quick question. Can I do blood allergy testing while on antihistamine?

[crystalfresh]

First food allergy testing was done with Intradermal and Scratch testing. Now I am taking *blood* for allergy testing.

Should I:
  A. Retest foods to rule out false pos.
  -or-
  B. Test foods that showed up negative with skin testing?

Not enough blood drawn to retest both.

Please answer by 4pm Est time 8/22/08 Friday if possible to put on the order. Thanks.

[Bhupinder Kaur, MD]

Hello,

RAST allergy testing can be used to determine IgE reactions to foods and items that are airborne called “inhalants,” such as dust mites, pollen, animal dander and molds. An advantage of the RAST test is that it’s not affected by antihistamines or other medications  that the patient may be taking.This is not the case in skin ***** or patch test.
http://www.cumc.columbia.edu/dept/pulmonary/4ClinicalPage/Clinical%20Centers/Website/allergytesting.htm
Variations of the RAST include FAST (fluoro-allergosorbent test) and MAST (multiple antigen simultaneous testing).They can also be used for allergy testing.

Positive skin or RAST tests help narrow the list of suspected allergens, but don’t often point directly to the cause of symptoms. A challenge test may also be needed esp in food allergies.Blood test like RAST are costlier than the skin tests.Pls discuss with your doctor the options of food elimination and food challenge tests.

Take care and regards.

[shot]

I've always heard the RAST test was not very reliable at all.  A blood test is supposed to be more reliable but both do not pinpoint foods which do not cause IgE reactions.  I don't understand why some foods do and others don't but it means that some foods you may be allergic to don't show up on either test.  I agree that at least the tests give you a starting point.  I have an appt to get the skin testing for food done.  Good luck.