What Allergy Sufferers Need to Know
Each spring, summer and fall, plants release tiny pollen grains to fertilize other plants of the same species. Most of the pollens that cause allergic reactions come from trees, weeds and grasses. These plants make small, light and dry pollen grains that are carried by the wind.
Among North American plants, grasses are the most common cause of allergy. Ragweed is a main culprit among the weeds, but other major sources of weed pollen include sagebrush, pigweed, lamb’s quarters and tumbleweed. Certain species of trees, including birch, cedar and oak, also produce highly allergenic pollen.
People with pollen allergy only have symptoms for the period or season when the pollen grains to which they are allergic are in the air. For example, in most parts of the U.S., grass pollen is present during the spring.
A pollen count, which is often reported by local weather broadcasts or allergy websites, is a measure of how much pollen is in the air. Pollen counts tend to be highest early in the morning on war, dry, breezy days and lowest during chilly, wet periods. Although pollen counts reflect the most-recent 24 hours, they are useful as a general guide for when it may be wise to stay indoors with windows closed to avoid contact with a certain pollen.
–Source: National Institute of Allergy and Infectious Diseases