Many people associate hay fever with springtime, but it can occur anytime plants release pollen. A notorious autumn offender is ragweed, from the genus Ambrosia. This plant is responsible for about half of all cases of allergic rhinitis attributable to pollen.

Ragweed can grow just about anywhere, but is most common in the Midwest and Eastern states. Ragweed season begins in August when it first blooms and releases pollen; the season may last until November, with peak counts usually occurring in September. Pollen is dispersed by the wind and because the grains are very fine and light, can remain airborne for days and may travel hundreds of miles. Pollen counts are highest on warm, windy days, and between the hours of 10 AM and 3 PM. They tend to be lowest on cool, wet days.

Hay fever symptoms include stuffy or runny nose, sneezing, itchy eyes and throat, and hives. People with ragweed allergies may suffer from a related food allergy known as oral allergy syndrome, which causes itching, burning, and swelling in the mouth and throat when certain foods are ingested. Bananas, cantaloupe, melons, beans, potatoes, celery, cucumbers and other foods are common triggers.

Treatment for ragweed allergies includes over-the-counter antihistamines and decongestants and nasal steroid sprays. Those whose symptoms do not respond to medications may want to undergo allergy testing; once an allergy to ragweed is verified, immunotherapy (allergy shots) may be an option for long-term control.