It’s a top ranking that Knoxville, Tenn., won’t be promoting any time soon: It’s No. 1 on the list of “most challenging” places to live if you have spring allergies. That’s according to the Asthma and Allergy Foundation of America’s 2010 ranking of 100 U.S. cities.
The city earned the dubious honor on the latest list of "The 100 Most Challenging Places to Live with Spring Allergies." Los Angeles, much maligned for its air pollution, ranked far better -- number 92 on the 2010 list. San Diego was 99, and Harrisburg, Pa., came in at number 100. (See full list at the end of this article)
What do the worst allergy cities have in common? What makes a city good for people with allergies? Unfortunately, there are no easy answers. But allergy experts say there are key factors to look for.
How the 'Worst' Allergy Cities Are Computed
Unveiling the worst spring allergy cities in America has become an annual tradition. The lists are released by the Asthma and Allergy Foundation of America, in Washington, D.C., and many factors are plugged in to figure out which cities will get the dubious honor each year, says Mike Tringale, a spokesman for the foundation.
The foundation experts look at the most populated cities and take into account factors such as the region's pollen score (pollen count and other factors), along with the number of allergy medications prescribed and the number of board-certified allergists practicing there. Each city gets a score and then the list of 100 cities is drawn up.
More than half of the top 10 worst cities are Southern cities: Knoxville, Tenn.; Louisville, Ky., Chattanooga, Tenn.; Charlotte, N.C.; Greensboro, N.C.; and Jackson, Miss.
But Philadelphia; St Louis; Dayton, Ohio; and Wichita, Kan., are also in the top 10.
Why Are Some Cities Worse for Allergies Than Others?
"The fundamental issue with cities is the type of plant or grasses, trees or weeds that grow in the area," says Daniel Waggoner, MD, an allergist in Mystic, Conn., who is not affiliated with the list creation but is familiar with it.
Cities with an exceptionally high concentration of trees, grass, or weeds may have more pollen in the air, he says. Local environmental factors such as wind, humidity, typical temperatures -- and air pollution -- also play a role in allergies, notes Miguel Wolbert, MD, an allergist in Evansville, Ind. and a certified pollen counter.
What if you don't live in a major city? How can you tell if your region is especially bad for allergies? Here's what the experts have to say.
Allergy Risks by Geography
Near River Basins
"If you are around certain river basins, such as in Ohio or Mississippi, higher pollen counts occur due to high humidity levels," says Wolbert. Pollen thrives in high humidity, he says.
In the middle of Mississippi, everything sits, Wolbert says, so pollen is likely to be worse.
Plants around river basins vary in different parts of the country. For instance, in the lower Mississippi, ragweed and chenopods thrive, Wolbert says.
In the Mountains
In the mountains, there are fewer plants, Wolbert says, perhaps explaining why some mountainous states are absent from the list. "The higher the mountains, the fewer the plants,'' Wolbert says, resulting in less pollen overall.
And pollen from evergreens is typically heavy pollen, so it falls to the ground relatively quickly, he says. It poses less of an allergy problem simply because it is airborne for a shorter time.
Near the Coast
While some seaside towns made the list, in general a sea breeze helps reduce allergens, Leftwich says. The closer to the sea the better. "If you can afford to live in that first quarter mile from the beach, it's great. Pollens are not so much a problem there."
In coastal areas that are densely populated, however, the pollution can make allergies worse despite the sea breeze, Wolbert says. One exception: In Miami, he says the sea breeze is strong enough to reduce pollen-triggered allergies, despite the population.
Allergy Risks by Region of the U.S.
It's difficult to pick out one region of the country as "better" or "worse" for allergies, according to the experts. Why? Even within a region the trees, grasses, and weeds that typically provoke allergies can differ.
People's sensitivities are very different, too. For example, one person may be allergic to tree pollen. Another person may be allergic to grass pollen. Your allergies react to the plants that surround you, no matter the region of the country. Nonetheless, here are allergy triggers to look for, region by region.
The Midwest, known for its ragweed pollen, has several cities on the list including Dayton, Ohio, and St. Louis. Some experts believe global warming is making the ragweed season longer, Wolbert says, so pollen may just get worse.
''Ragweed thrives with higher carbon dioxide,'' he says. So the more air pollution, the hardier ragweed becomes. "I think ragweed will continue to worsen every year," he says.
Global climate change also appears to increase ragweed – and allergic disease – according to recent studies in medical journals, including the Journal of Allergy and Clinical Immunology.
In the Midwest -- Illinois, Indiana, Ohio, Minnesota, Wisconsin, Michigan, Iowa, Missouri -- tree pollen season is roughly March to June. Trees that typically trigger allergies include elder, alder, birch, oak, elm, and hickory, Wolbert says.
Overlapping the tree pollen season, grasses start to pollinate in the summer, Wolbert says. Grasses that can provoke allergy symptoms include Bermuda, Timothy, fescue, rye, and orchard grass.
Weeds pollinate in the fall, says Wolbert. "Weed season is pretty uniform," he says. The Midwestern states are known for lamb's quarter weed, pigweed, Russian thistle, and others.
In Washington, Oregon, and California, tree pollination is usually in full swing from February to June. Trees that are native cause the most allergy problems, says Richard W. Honsinger, MD, an allergist in Los Alamos, N.M., and a clinical professor of medicine at the University of New Mexico School of Medicine.
For instance, in the Pacific Northwest, pollen from the native alder and birch trees can make people with allergies miserable, he says.
In California, oak and walnut trees can be problematic for those with allergies, he says. Pine trees don't deserve their bad reputation, he says. "People always think pine pollen causes problems because they see it." When they park their car under pines in the mountain, he says, the car can be covered with the pollen.
"But pine is a heavy pollen, it falls to the ground," he says."It is airborne, but it settles. It doesn't float in the air as long so it doesn't provoke as strong an allergy attack."
In the dryer states of Arizona and New Mexico, trees such as cedar, ash, and oak pollinate from about February to April, Honsinger says.
Grass pollination in the West is high in May and June, Honsinger says. Bermuda grass, orchard, wheat grass, and fescue are common in the West. Honsinger says, "If you are allergic to one grass, you are often allergic to almost all," with one exception. People allergic to Bermuda grasses are often allergic only to those, he finds.
Weed season in the West can extend from spring or early summer through fall. Among the offenders: plantain weed. Ragweed is not so much a problem in the Pacific Northwest and northern California, but it can be in Arizona and New Mexico. Ragweed can grow throughout the U.S., according to the Asthma and Allergy Foundation of America.
When it comes to allergies, Leftwich says, "Tennessee is where everything comes together," noting there are several different types of pollen flourishing there. His town, Nashville, Tenn., made No. 47 on the list.
Nashville has plenty of Southern state company on the worst cities for allergies list, and for reasons that make sense, Leftwich says. ''The longer the growing season, the worse it is for allergies," he says.
A second factor is rainfall. So people with allergies who live in a Southern city with a temperate climate, long growing season, and plenty of rain can expect to sneeze a lot.
In the south, tree pollen season is roughly February through May, with pollens from oak, cedar, and pecan trees the worst allergy triggers. Birch and hickory trees can also provoke allergies, Leftwich says.
"Grasses can be a problem in the South year round," he says. Commonly planted grasses include fescue, rye, and bluegrass. Never mind the type. Often, someone who is allergic to one of those will be allergic to all, he says.
Weed season kicks in around late summer and continues until a hard freeze, Leftwich says. The biggest culprit: ragweed.
In the Northeast -- states such as Maine, New York, Pennsylvania, Delaware, Connecticut, and others -- tree pollens begin in February or March, continuing through June or so, says Clifford Bassett, MD, an allergist in New York City. Among the offenders: elm, hazelnut, maple, poplar, hackberry, and red cedar.
In May and June, grass pollens kick up. While some people are only allergic to Bermuda grass, most with allergies are allergic to all grasses.
Weed season begins in August and continues through the fall. Pollens from such weeds as English plantain, lamb's-quarter, and cocklebur provoke symptoms, Bassett says.
Putting the Worst Allergy Cities List Into Perspective
Waggoner and other allergists caution that the list of worst cities for springtime allergies may not be that scientific. "The worst city for one person is the best city for another person," Leftwich agrees. "It depends on what you are allergic to."
"Being allergic to one tree pollen doesn't mean you are allergic to another." The city that has the worst tree pollen count may not have the worst grass pollen count, he says. “It is a common misconception that pollens are pollens. They are not."
No scientific studies have thoroughly compared allergy risks in different cities, Leftwich says. Instead, we turn to the annual list almost for bragging rights.
So how can we use the annual list of worst allergy cities? Well, don't use the list to pick one place to live over another, allergy experts say. Instead, get allergy testing to be sure you know what triggers your allergies. And if you must move, find out whether your pollen triggers grow widely in the area and neighborhood you're considering.
What if you love your home, but you're in a bad allergy community? Talk to your doctor. There are preventive treatments you can start before allergy season to help you stay home and healthy.
Complete List of 2010 Spring Allergy Capitals
1. Knoxville, Tenn.
2. Louisville, Ky.
3. Chattanooga, Tenn.
4. Dayton, Ohio
5. Charlotte, N.C.
6. Philadelphia, Pa.
7. Greensboro, N.C.
8. Jackson, Miss.
9. St. Louis
10. Wichita, Kan.
11. Madison, Wis.
12. Columbia, S.C.
13. Richmond, Va.
14. Providence, R.I.
15. Birmingham, Ala.
16. Memphis, Tenn.
17. Oklahoma City, Okla.
18. Baton Rouge, La.
19. Allentown, Pa.
20. New Orleans
21. New York
22. Syracuse, N.Y.
23. Augusta, Ga.
24. Little Rock, Ark.
25. McAllen, Texas
26. Columbus, Ohio
27. Hartford, Conn.
28. Greenville, S.C.
29. Rochester, N.Y.
30. Springfield, Mass.
31. Pittsburgh, Pa.
32. Scranton, Pa.
33. Tulsa, Okla.
34. Omaha, Neb.
35. Buffalo, N.Y.
36. Des Moines, Iowa
37. Toledo, Ohio
38. Akron, Ohio
39. Virginia Beach, Va.
40. Poughkeepsie, N.Y.
41. Albany, N.Y.
42. San Antonio
43. Washington, D.C.
44. Kansas City, Mo.
45. Tucson, Ariz.
46. Portland, Maine
47. Nashville, Tenn.
49. Cleveland, Ohio
51. Charleston, S.C.
53. Youngstown, Ohio
54. Las Vegas
55. Jacksonville, Fla.
56. New Haven, Conn.
58. Cincinnati, Ohio
60. Grand Rapids, Mich.
62. El Paso, Texas
63. San Francisco
64. Modesto, Calif.
65. Lancaster, Pa.
66. Milwaukee, Wis.
67. San Jose, Calif.
69. Cape Coral, Fla.
70. Tampa, Fla.
71. Raleigh, N.C.
72. Lakeland, Fla.
73. Bakersfield, Calif.
74. Bridgeport, Conn.
75. Portland, Ore.
76. Worcester, Mass.
77. Orlando, Fla.
78. Austin, Texas
79. Albuquerque, N.M.
80. Ogden, Utah
81. Phoenix, Ariz.
84. Riverside, Calif.
85. Salt Lake City
86. Stockton, Calif.
88. Sarasota, Fla.
89. Sacramento, Calif.
90. Palm Bay, Fla.
91. Colorado Springs, Colo.
92. Los Angeles
94. Fresno, Calif.
95. Oxnard, Calif.
97. Boise City, Idaho
98. Daytona Beach, Fla.
99. San Diego
100. Harrisburg, Pa.