Histamine released from whole blood was determined by an automated fiuorometric histamine analysis system. The increased release of histamine from basophils by anti-IgE was observed in ten healthy subjects and 12 extrinsic asthma patients, while the release in 11 intrinsic asthma patients was significantly less as compared to that in healthy and extrinsic asthma subjects. House dust extract caused a significant increase in the histamine release from basophils of the extrinsic asthma patients who are sensitive to house dust. It was concluded from this study that histamine released from basophils could be easily determined by an automated analysis system and that the
method is useful for the diagnosis and study of allergy.