Outdoor allergies (also called “seasonal allergic rhinitis” or “hay fever”) are allergies to common airborne particles that are found outside. When inhaled, the allergen causes symptoms that may include a runny nose, congestion, sneezing, and sinus pressure. Examples of outdoor allergens include mold spores and pollen from trees, grasses, and weeds. Of course, other allergens can be encountered outdoors, such as bee venom and dust for example, but outdoor allergies usually refer to allergies caused by plant material or fungi.

Outdoor allergies tend to occur in the spring, summer, and fall, when plant pollen is more prevalent. People are sensitive to different allergens and people with seasonal allergies may experience symptoms of differing severity that peak at different times of the year. Outdoor allergies also tend to depend on where in the country you live; you may have very severe allergies in one place and almost no symptoms in another.

According to the American Academy of Allergy, Asthma, and Immunology, outdoor allergies affect more than 35 million people in the United States.