Biorhythmic changes of plasma histamine levels in healthy volunteers.

The plasma histamine levels were reported to increase in early hours of the morning in asthmatic patients. It was supposed that this phenomenon would also be observed in normal volunteers. In this study using twelve normal healthy volunteers the plasma histamine levels were examined in a pharmacokinetic manner. It could be shown that plasma histamine levels flow biorhythmic changes with 3 maxima and 3 minima. The acrophases of the maxima are 12.77 +/- 0.61, 19.33 +/- 0.78 and 5.42 +/- 1.83 h. The most important rise in plasma histamine levels was found in the early hours of the morning representing about 55% of the total histamine available in plasma.