[Skip to Content]

Definition: Pollen


During the spring, summer, and fall, plants release pollen (a fine powder that is carried by the wind from plant to plant in order to fertilize them). Each microscopic grain of pollen contains proteins that can cause allergic reactions when breathed in. These proteins can trigger asthma symptoms. Grasses, trees, and weeds (such as ragweed) are most often responsible for causing allergies.