Things that cause asthma episodes are known as triggers. Many asthma triggers are found outdoors.
Air pollution can trigger asthma. Even healthy people can have trouble breathing on high air pollution days. The main air pollution triggers are small particles (also known as particulate matter) and ground level ozone. These triggers come from:
Cold air, humid air, and changes in the weather can trigger asthma.
Not all people with asthma have allergies, but for those who do, outdoor allergens may trigger asthma. Common outdoor allergens that trigger asthma episodes include:
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