Histamine-mediated mechanisms in the human nasal airway

The nasal actions of histamine were originally attributed to vascular and neuronal H1 receptor activation. Recent studies have identified a H3 receptor that contributes to histamine-induced inflammation via the inhibition of sympathetic activity. There is also evidence that pollen-induced nasal blockage can be treated by H1 antagonists. However, although desloratadine might offer relief, this is unlikely to be through inhibition of nasal H1 receptors. Despite evidence of an active H2 receptor on nasal vasculature, this receptor subtype appears to play only a minor role in nasal inflammation. The activation of H1 receptors cannot account for all of the acute actions of histamine in the nasal airway.