Abstract e nature of basophil activation as an ex vivo chal-lenge makes it a multifaceted and promising tool for the allergist. rough the development of ow
cytometry, discovery of activation markers such as CD63 and markers identifying basophil granulo-cytes, the basophil activation test (BAT) has be-come a pervasive test. BAT measures basophil re-sponse to allergen crosslinking IgE on between 150 and 2,000 basophil granulocytes with remarkable analytical sensitivity in < 0.1 ml fresh blood. Dicho-tomous activation is assessed as the fraction of re-acting basophils. In patients with food-, insect ven-om-, and drug allergy and patients with chronic urticaria BAT can be part of the diagnostic evalu-ation in addition to history, skin prick testing, and speci‡c IgE determination. BAT may also be help-ful in determining the clinically relevant allergen. Basophil sensitivity may be used to monitor pa-tients on allergen immunotherapy, anti-IgE treat-ment, or in the natural resolution of allergy. e
test may use fewer resources and be more reproduc-ible than oral, sting, nasal or bronchial challenge testing. BAT may be useful before challenge testing
as it is less stressful for the patient and avoids se-vere allergic reactions. It may be useful before chal-lenge testing. An important next step is to stan-dardize BAT and make it available in diagnostic laboratories. is article provides an overview of the practical and technical details as well as the utility of BAT in diagnosis and management of allergic diseases.