Allergic rhinitis is linked to the development of asthma. Following allergen exposure, fibroblast progenitors, or fibrocytes, are increased in the blood and bronchial mucosa in asthma. As shown in non-asthmatic patients with allergic rhinitis, these cells may play a role in lower airway remodeling. For a study, researchers sought to see how seasonal allergen exposure affects blood circulating fibrocytes in allergic rhinitis patients who didn’t have asthma. Blood was taken from non-asthmatic patients with seasonal allergic rhinitis at baseline and the peak of symptoms. Flow cytometry evaluated cells stained for fibrocyte markers (CD34, CD45, CXCR4, collagen I). The data was analyzed from 26 participants (11M:15F) aged 29 and 8 years. During the pollen season, there was a substantial decrease in blood fibrocytes in patients sensitised to trees compared to baseline [median (25–75 percentile), 9.3 (6.4–20.7)% vs 7.0 (4.2–10.1)%, P=0.007] showed a significant rise in grass-sensitive subjects [12.7 (9.9–23.1)% vs 64.0 (57.6–73.6)%, P<0.001] and ragweed-sensitive subjects [8.0 (7.4–10.8)% vs 48.2 (43.5–52.6)%, P<0.001]. Between the 2 visits, there was a substantial drop in CXCR4 mean fluorescence [1814 (1261–2235) vs 1352 (814–1796) (arbitrary units), P=0.02. These results help to demonstrate dynamic changes in blood fibrocyte activation and migration into the airways after natural allergen exposure. The results could point to 1 of the elements that contributed to the development of asthma in allergic rhinitis patients.