- assess the in VITRO basophil activation induced by aspirin before and after desensitization procedure by flow cytometric cellular allergen test using basophils surface marker and mediators' dosage. Before the challenge procedure these tests aim to confirm the clinically established diagnosis of hypersensitivity. After desensitization, these tests intend to better assess the efficiency of the induced tolerance, to attempt to identify predictors of successful desensitization as well as identify potential cross reactivity with other NSAIDs..