The attention which has been paid in recent years to the problems of hay-fever has clearly established the exciting cause in the noxious pollen of a variety of plant forms. The species involved have in common the feature that they are all wind-pollinated, so that the large quantity of pollen that they produce is distributed by the air and can readily reach the nasal passages. Scheppegrell1 has pointed out that the responsibility of the noxious plants for hay-fever depends, first, on the proximity of these plants, and, secondly, on the size of the pollen, which has an effect on their buoyancy. For example, the pollen of corn, though very toxic, is rarely responsible for hay-fever because the comparatively large size of the particles (80 microns) limits the potential area of its distribution to a few yards from the plant; whereas the pollen of the common ragweed (measuring only 15
HAY-FEVER AND POLLEN. JAMA. 1917;LXIX(7):566. doi:10.1001/jama.1917.02590340066013
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