Pollens and mold spores are common outdoor allergens that can trigger the allergic symptoms of hay fever such as sneezing, runny nose, itchiness in the nose, throat, eyes and ears, and congestion. Typically it is the small light pollens of trees, weeds and grasses, readily disseminated by wind currents, that are associated with hay fever allergy symptoms. Different pollinating periods throughout the spring and summer are associated with different plant groups. Trees, for example, usually pollinate earliest, from late January into May. Grasses are next, usually beginning in May and continuing until mid-July.
Weeds are later, and usually pollinate from late summer into early fall.
Molds are microscopic fungi similar to mushrooms and mildew, but lack any stems, leaves or roots. The spores of mold are similar to pollen, being light and easily carried by wind and air currents. The occurrence of mold spores is mostly affected by weather conditions such as temperature, moisture, humidity levels, and wind. Mold spores can occur year round in the South and West Coast, and originate from a wide variety of indoor and outdoor sources. Mold and Pollen Counts.