Increased urinary excretion of 1.4-methyl-imidazoleacetic acid in patients with atopic dermatitis

To investigate whether the overall histamine turnover is increased in patients with atopic dermatitis, without respiratory disease, the urinary excretion of the main histamine metabolite 1.4-methyl-imidazoleacetic acid (MIAA) was examined in 23 patients and in 23 age- and sex-matched non-atopic controls. The patients excreted significantly more MIAA than the controls. One third of the patients however, showed MIAA excretion within or below normal range. The MIAA excretion was neither correlated to the severity of the eczema nor to the total serum IgE. It was concluded that histamine does not play a significant role in the pathophysiology of atopic dermatitis, and that the great variation in MIAA excretion, and hence the histamine turnover, reflected the spectrum of histamine releasability in the patients.