Generally smaller in diameter than a human hair, pollen particles are the male reproductive cells of flowering plants. While pollens from bright flowers are usually carried from plant to plant by insects, many trees, grasses and weeds rely on wind to carry their light, dry pollen. These are the ones that trigger allergic reactions. The trouble comes from trees in the spring, grasses in June and weeds in late summer.
Allergy Associates of La Crosse reports pollen data gathered on the rooftop at Mayo Clinic Health System’s La Crosse campus — generally from April through September. Readings last week were as high as 400 grains per cubic meter, a concentration not usually seen until the peak time of May.
Sources: National Allergy Bureau and Allergy Associates of La Crosse