Spring is prime time for allergies, and certain U.S. cities are harder hit than others, according to the Asthma and Allergy Foundation of America (AAFA).

Every year, the AAFA lists the 100 worst cities for springtime allergies. Here are the top 10 cities on this year’s list, along with last year’s rankings:

1. Hartford, Conn. (last year: 49)

2. Greenville, S.C. (last year: 6)

3. Boston (last year: 47)

4. Detroit (last year: 80)

5. Orlando, Fla. (last year: 56)

6. Knoxville, Tenn. (last year: 11)

7. Omaha, Neb. (last year: 17)

8. Sacramento, Calif. (last year: 62)

9. Washington, D.C. (last year: 16)

10. Baltimore (last year: 58)

Curious about where your city ranks? The AAFA's full list of the 100 worst allergy cities, click here.

WebMD Tool: Check Your Local Pollen Count

About the List

The top cities on last year’s list were located in the Southeast. But allergies are a nationwide problem, and the rankings can change from year to year. For instance, last year’s leader -- Lexington, Ky. -- is in the 75th spot on this year’s list.

Rankings are based on three factors: pollen scores, the number of allergy medications used per patient, and the number of allergy specialists per patient.

Funding for the AAFA’s new list came from Procter & Gamble, Schering-Plough, and pollen.com.

Proctor & Gamble and Schering-Plough both make allergy-related products. Pollen.com is a division of Surveillance Data Inc., a private company that researches health care and consults for the pharmaceutical and consumer products industries.

Learn How to Conquer Your Allergies

Seeking Relief

Consult a doctor to get your allergies diagnosed and treated.

If you’re allergic to pollen, close the windows at home and in your car. If you need to cool down, run the air conditioning instead of opening the windows. Put the air on “recirculate” so you’re not bringing in outside air filled with pollen.

As many as 50 million people in the U.S. have allergies, and nearly 36 million of them have hay fever (a seasonal allergy to pollen), according to the American Academy of Allergy, Asthma & Immunology.

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By Miranda Hitti, reviewed by Louise Chang, MD

SOURCES: Asthma and Allergy Foundation of America: “The 2006 Spring Allergy Capital Rankings.” News release, Asthma and Allergy Foundation of America. WebMD the Magazine: “Plagued by Pollen.”