allergy blood test, a blood test used to measure serum immunoglobulin E, which is an effective method of diagnosing allergy and of specifically identifying the allergen. This test can be helpful when the results of an allergy skin test are questionable, when the allergen is not available in a form for dermal injection, when the allergen may incite an anaphylactic reaction if injected into the patient, or when skin testing is particularly difficult (for example, in infants or patients with dermographia or widespread skin disease).
