Pollen is a fine powder produced by certain plants. During the spring, summer, and fall seasons, it is released into the air and picked up by the wind. The wind carries it to other plants so they can make seeds. But while it's traveling in the wind, pollen gets into the air we breathe. Many people are allergic to it, including people who have asthma. When they breathe in pollen, it can trigger their asthma symptoms.