[Circadian regulation of urticaria and anaphylaxis]

IgE-mediated immediate-type allergic reactions in the skin show a diurnal rhythm, although the regulatory mechanisms are poorly understood. In mammals, the circadian rhythms are driven by the circadian clock system consisting of the light-entrained central clock located in the suprachiasmatic nucleus(SCN) of the hypothalamus and peripheral oscillators present in nearly all cell types. We have recently shown that the circadian clocks drive the daily rhythms of IgE-mediated allergic reactions in the skin by using a passive cutaneous anaphylactic reaction model in mice. We also found that systemic anaphylactic reaction shows a time of day-dependent variation, which relied on the circadian clocks. These findings highlight the circadian clocks as an important regulatory component of local and systemic allergic reaction.