FRIDAY, Sept. 2 (HealthDay News) -- A trend toward a longer allergy season may mean more sneezing, sniffling and misery for allergy sufferers, experts say.

Allergy season used to run from mid-August through September, but in many parts of the country, symptoms such as itchy eyes and stuffiness are starting earlier and extending through October, according to the American Academy of Allergy, Asthma & Immunology (AAAAI).

The main culprit behind the seasonal misery: ragweed. One ragweed plant can make up to 1 billion pollen grains, especially bad news for those who suffer from hay fever or allergic rhinitis.

Research suggests this prolonged window for allergies is the result of rising temperatures and higher carbon dioxide levels, which help allergen-producing plants grow for a longer period of time, according to an AAAI news release.

Getting a proper diagnosis and finding out exactly what patients are allergic to is the first step in managing symptoms that can include, in addition to the sneezing and stuffy nose, an itchy throat or a worsening of asthma symptoms, experts advised.

The best way for allergy sufferers to feel better is to avoid contact with pollen altogether. The group recommends avoiding the outdoors when the National Allergy Bureau reports that pollen counts are particularly high.

More information

The National Institute of Environmental Health Services provides more information on ragweed pollen.