Blood tests measure the amount of IgE antibody circulating in the blood. The test is carried out on a small sample of blood, usually taken from a vein in the arm in the usual way. The sample is then sent to a laboratory and the results are available in 7 to 14 days
In general, these tests are not specific to a particular allergen and are therefore not easy to interpret; both false positive and false negative results are possible, and the presence of IgE in a test does not necessarily mean that the substance is actually causing the patient’s symptoms. For these reasons, these tests are not recommended.
Interpreting the results requires care and experience and should always be done by a trained clinician in conjunction with the clinical history.