Priming effect of a birch pollen season studied with laser Doppler flowmetry in patients with allergic rhinitis

Nasal mucosal provocation tests were done on eight patients with seasonal allergic rhinitis before and after a birch pollen season. The effects on nasal microvascular blood flow were detected by means of laser Doppler flowmetry. The patients reacted to the birch pollen provocation with an increase in blood flow. This increase was greater after the pollen season than before, when the same pollen doses were used, indicating a priming phenomenon of the resistance vessels.