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Pollens are the tiny, egg-shaped male cells of flowering plants. Pollens from plants with bright flowers, such as roses, usually do not trigger allergies. These large, waxy pollens are carried from plant to plant by bees and other insects. Many trees, grasses and low-growing weeds have small, light, dry pollens that are well-suited for dissemination by wind currents. These are the pollens that trigger allergy symptoms.
A pollen count is the measure of the amount of pollen in the air. Pollen counts are commonly included in local weather reports and are usually reported for mold spores and three types of pollen: grasses, trees, and weeds. The count is reported as grains of pollen per square meter of air collected over 24 hours. This number represents the concentration of all the pollen in the air in a certain area at a specific time. The pollen count is translated into a corresponding level: absent, low, medium or high.
In general, a "low" pollen count means that only people extremely sensitive to pollen will experience symptoms. A "medium" count means many people who are relatively sensitive to pollen will experience symptoms and a "high" count means most people with any sensitivity to pollen will experience symptoms.
Although the pollen count is an approximate value and fluctuates, it is useful as a general guide when you are trying to determine whether or not you should stay indoors to avoid pollen contact.