Skin testing with bendamustine: what concentration should be used?

We present a case of the patient, who developed hypersensitivity reaction during the treatment of chronic lymphocytic leukemia. Bendamustine was suspected as a culprit agent. The patient as well as 3 controls underwent skin testing with the concentrations of the bendamustine described in earlier studies. We doubted the testing recommendations as all the controls developed serious local reactions. The clinical meaning of the positive skin test reaction in the patient remained unclear and questioned the safeness of recommended testing concentrations as in certain situations wrong diagnosis could be made or even harm could be done. Future investigations are needed when allergy to bendamustine is suspected.