[Twenty-four hour evaluation of urinary N-methylhistamine excretion and age-dependent changes in non-atopic children].

Urinary N-methylhistamine (NMH) of the histamine metabolite was determined in non-atopic children to investigate the circadian rhythm and age-dependent changes. Over a period of 24 hours, urinary NMH levels were 330 +/- 37 micrograms/g Cr (Mean +/- SE) in the early morning, 396 +/- 35 in the morning, 398 +/- 31 in the afternoon and 464 +/- 35 at night in fourteen non-atopic children (aged 2 months-2 years, Mean = 11.9 months, M:F = 10:4). The early morning NMH levels were lower than the night levels (p < 0.05). Age dependent changes in urinary NMH levels were 482 +/- 27 micrograms/g Cr (Mean +/- SE) in the 3-5 month group, 450 +/- 37 in the 6-8 month group, 382 +/- 26 in the 9-12 month group, 332 +/- 29 in the 1-2 year group and 334 +/- 33 in the 2-5 year group in fifty-five children (aged 3 months-4.5 years, Mean = 1.2 years, M:F = 36:19) who had no allergic symptoms. Urinary NMH levels at 3-5 months were higher than those at 9-12 months, 1-2 years and 2-5 years (p < 0.05, p < 0.005, p < 0.01), and NMH levels at 6-8 months were higher than they were at 1-2 years and 2-5 years (p < 0.05, p < 0.05). In conclusion, to diagnose food hypersensitivity or histamine-induced allergic reactions in children from urinary NMH levels, it is necessary to consider the circadian rhythm and age-dependent changes in urinary NMH levels.