Correlation between urinary levels of histamine metabolites in 24-hour urine and morning urine samples of man: Influence of histamine-rich food

In this study, we have determined and correlated the excretion of the 2 most important histamine metabolites, N-methylhistamine and N-methylimidazoleacetic acid, in 24-hour urine and morning urine samples of 14 normal healthy persons. We found no significant difference between morning urine and 24-hour urine samples, provided that the subjects were on a histamine-poor diet for at least 24 hours. We also studied the influence of the consumption of histamine-rich foodstuffs on the reliability of these parameters. The morning urinary N-methylhistamine excretion is less affected by histamine-rich foodstuffs and therefore proposed to be the most reliable parameter for endogeneous histamine release.