Grapefruit Allergy Blood Test in California

What this test measures

An allergy to grapefruit is a form of IgE-mediated food allergy, in which the immune system treats proteins in the fruit as a threat and releases antibodies and histamine. The grapefruit allergy test detects those circulating IgE antibodies in serum. Because reactions to citrus can range from mild oral itching to more significant swelling, the result is reviewed together with the symptoms and timing of exposure.

The sample required is a small venous blood draw, which is analyzed for grapefruit-specific IgE. Laboratories report the antibody level in a standardized unit and usually assign a semiquantitative reactivity class. Some panels also report total IgE and markers of cross-reactivity, since proteins shared between citrus fruits, pollens, and other plant foods can produce positive results without clinical symptoms.

People often order this test after noticing itching, tingling, or hives around the mouth after eating grapefruit or drinking citrus juice. It can also be included when a broader food allergy profile is being assembled. A healthcare provider can combine the laboratory finding with an exposure history to decide what it means for daily eating.