A differential amplifying circuit 11 includes a current mirror circuit having first and second current ends to which drains of MOS transistors M8 and M9 are respectively connected, and a pair of differential MOS transistors M1 and M2 having gates between which a switch SW1 is connected. The first computing service can send a message that includes the session token through a passive client to the second computing service. The present invention further demonstrates compositions that include famotidine are effective at treating symptoms associated with a flush reaction in subjects that are not significantly responsive to treatments with the H1 antagonist loratidine or the H2 antagonist cimetidine.