Changes in nasal mast cell numbers in and out of the pollen season.

Mast cells were counted in biopsies of the nasal mucous membrane from 8 patients with allergic rhinitis during (July 1985) and after (October 1985 and January 1986) the grass pollen season in both the superficial epithelium and the deeper lamina propria. There was an eightfold increase in the total number of mast cells in the nasal mucous membrane during the grass pollen season when compared to midwinter. In addition, there was a striking change in the number of mast cells present in the surface epithelial layer from almost total absence in biopsies taken in midwinter to counts of between 2,000 and 28,000/mm3 in all but 1 patient during the summer.