Report Reveals U.S. Allergy Hotspots

If you're sensitive to pollen, you might want to avoid Louisville, Ky., during allergy season.

The Asthma and Allergy Foundation of America has released the United States' top 50 "Allergy Capitals."

To determine the rankings, the foundation looked at the average recorded pollen levels over the last seven years and the length of the peak season for pollen. They also considered the number of antihistamine prescriptions written per capita in the last year and the number of board-certified allergists per capita.

Louisville tops the list of allergy hotspots, followed by Austin, Texas, St. Louis, Atlanta, and Charlotte, N.C. Full List

The report comes during the worst part of allergy season in many parts of the country, as pollen counts are skyrocketing.

"Allergic rhinitis, or hay fever, is triggered by allergens, substances that initiate an allergic response, such as pollens or molds," said Dr. Jay Portnoy, of the American Academy of Allergy, Asthma & Immunology. "Many trees, grasses and weeds have small, light and dry pollens that are easily carried by the wind, which is why allergy symptoms flare up in the spring."

Experts said allergy sufferers should know which allergens trigger their symptoms, and when to watch for them.

Trees pollinate earliest, from late February through May in most of the country, although this may fluctuate in different locations, according to the AAAAI. Trees that disperse allergens include oak, elm, birch, ash, hickory, poplar, sycamore, maple, cypress, walnut and western cedar.

Grasses follow next in the cycle, distributing their pollens May to July. Grasses to watch out for are timothy, Bermuda, orchard, red top and sweet vernal. In late summer and fall, weeds such as ragweed, sagebrush, pigweed, Russian thistle and cockleburr become problematic for allergy sufferers.

Although the period of pollination doesn't vary much from year to year, weather conditions can affect the amount of pollen in the air at any given time, experts say. The pollinating season starts later in the spring the further north one goes. Generally, the pollen season lasts from February or March through October.

If you suffer from allergies, experts say prevention may help you avoid trouble. They suggest staying indoors between 10 a.m. and 4 p.m. and on days with high humidity and high winds; keeping car windows closed while driving; and showering after spending time outdoors.

If you're following every prevention measure you know and you're still suffering from allergies, you may consider trying over-the-counter medications or visiting an allergist, experts said.

Full List: Top 50 Allergy Capitals