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Outdoor Asthma Triggers

Pollens, Molds, and Climate

By Kathleen MacNaughton, R.N., About.com

About.com Health's Disease and Condition content is reviewed by Sanja Jelic, MD

Outdoor asthma triggers are substances normally found outside that can set off asthma symptoms in sensitive people. Typical outdoor triggers include tree, grass, and weed pollen, mold spores, and certain extreme climate conditions. Let's take a closer look.

Tree, Grass and Weed Pollens

Timothy grass pollenSource: American Academy of Allergy, Asthma and Immunology
Pollen is an airborne allergen that may set off numerous asthma symptoms in sensitive people at certain times of the year. Pollen consists of tiny, egg-shaped male cells found in flowering plants. You may know pollen better as the tiny, powdery granules that plants use during the fertilization process.

Mold & Mold Spores

Mold and Mold SporesPhoto © A.D.A.M.
Mold can be both an indoor and an outdoor asthma trigger, depending on where you find it. Outdoor molds are found in piles of dead leaves, soil, vegetation and rotting wood.

Extreme & Changing Weather / Climate Conditions

Extreme weather conditions and changing climate conditions may also be an asthma trigger in certain people. For example, hot, humid weather alone sometimes sets off asthma symptoms in certain people. If you also live in areas where forest fires are common during the summer months or where a phenomenon known as an inversion happens during the winter months, then poor air quality may make things even worse.

Extreme cold can also be an asthma trigger, particular breathing in cold air. Also, changing weather conditions, such as changes in temperature and humidity, barometric pressure or strong winds may trigger asthma symptoms in some people.

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