Histamine in late asthmatic reactions following house-dust mite inhalation.

In order to investigate the role of histamine in the late asthmatic reaction (LAR) following house-dust mite (HDM) inhalation, we studied, with hourly intervals, urinary N tau-methylhistamine (an important metabolite of histamine) in 14 allergic asthmatic patients before and after broncho provocation with HDM. Four patients showed an early asthmatic reaction (EAR), while 10 patients developed a LAR as well. In the hour following the EAR a significant increase in urinary N tau-methylhistamine was observed as compared to the control day (0.01 less than p less than 0.05). During the LAR no increase of this metabolite was detected in the urine of the patients. Additionally, histamine was measured in broncho alveolar lavage fluid (BAF) obtained from 6 patients during the HDM-provoked LAR and compared to histamine levels in BAF from patients without a LAR, following broncho provocation. In the LAR group higher histamine levels were found than in the other patient and control groups. For the whole patient group no correlation was found between the degree of bronchial obstruction during the LAR and the BAF histamine values. No difference was found in N tau-methylhistamine in BAF between patients with LAR and controls. Thus histamine metabolite studies in the urine failed to provide evidence of involvement of histamine in the LAR, while further data are needed to interpret the results of local sampling in the lung.