BOSTON ( MainStreet) -- Here's a look at five U.S. cities that have big problems with congestion -- and we aren't talking about traffic.

We're talking about the presence of mold, pollen and other things that make the communities below America's worst places for nasal congestion, according to a recent study by Sperling's Best Places and Breathe Right Nasal Strips.

"Allergy sufferers should consider the findings of our study as a starting place in their search to find a place which may be more comfortable for them," researcher Bert Sperling says. "We wouldn't suggest anyone make a life-changing decision based solely on our research, but our findings do a great job of providing some insights so people can make their own best decisions."

Sperling's analysis is nothing to sneeze at.

He compiled his list by looking at such things as rates of smoking, influenza and use of prescription and over-the-counter allergy medicines.

He also studied humidity, rainfall, wind speed and other climate conditions that can promote the growth of mold spores, ragweed and other allergens.

Here's a look at the five cities at the top of his list, along with a rundown of each community's local economy and housing market. Home-price figures refer to properties listed on inside a given city or within approximately 20 miles of the community's borders.

Fifth-worst: Memphis, Tenn.
Median home price: $147,000
The home of B.B. King, Elvis Presley and other rock and soul musicians will have you singing the blues if you have breathing problems.

"Memphis had one of our study's highest scores for cold medication usage, and also one of the highest scores for allergens -- likely the result of the city's warm and moist climate," Sperling says. "On the bright side, ozone air pollution in Memphis is relatively low."

Real estate in the 1.3-million-person metro area is also doing fairly well, with median list prices on up 5.08% over the past year to $147,000 as of December. lists some 7,000 Memphis homes for sale, from $2,000 for a vacant two-bedroom home to $669,000 for a five-bedroom in the tony River Oaks neighborhood.

Located on the Mississippi River, Memphis has long been a transportation hub.

It hosts the Mississippi's second-busiest port, and also serves as corporate headquarters for FedEx Corp. ( FDX - Get Report)

Other companies that call Memphis home include AutoZone ( AZO) and International Paper ( IP - Get Report), as does the University of Memphis.

Fourth-worst: Louisville, Ky.
Median home price: $147,950
The former home base of tobacco giant Brown & Williamson, Louisville makes the list partly because it scores No. 1 among the nation's 50 largest cities for smoking.

Kentucky's largest city also has the second-highest score for allergens and a fairly high use of cold medicines, although flu incidence is low.

Located on the Ohio River, 740,000-population Louisville is perhaps best known as home to the Kentucky Derby, the Louisville Slugger baseball bat and Kentucky whiskey maker Brown-Forman ( BF.B - Get Report).

Health-insurance giant Humana ( HUM - Get Report) also calls Louisville home, as does fast-food giant Yum! Brands ( YUM - Get Report) -- parent of KFC, Pizza Hut, Taco Bell and other eateries.

As for housing, lists more than 9,400 Louisville-area homes for sale, priced from $4,900 for a two-bedroom short-sale home to $6.3 million for a 46-acre estate in nearby Prospect.

Median list prices rose 0.31% in 2011 to end the year at $147,950, according to the site.

Third-worst: New Orleans
Median home price: $170,000
Given New Orleans' tropical climate, it's not surprising Louisiana's largest city ranked in or near the top 20% for almost every congestion-producing factor studied. The only exception is air pollution, which isn't a significant problem in the Big Easy.

Located at the confluence of the Mississippi River and the Gulf of Mexico, New Orleans' economy focuses on shipping, energy and tourism.

Despite 2005's Hurricane Katrina, the 1.2-million-population city still boasts America's fifth-busiest port, major oil-and-gas operations and a tourist industry built around Mardi Gras and the French Quarter. New Orleans is also the home to Entergy ( ETR - Get Report) and Tulane University.

The New Orleans metro area's median list prices for homes dropped 4.5% over the past year to hit $170,000, according to

The Web site lists some 7,700 Greater New Orleans homes for sale. Properties range from a $79,900 four-bedroom home in Slidell to $12.5 million for the historic Robinson House estate.

Second-worst: Birmingham, Ala.
Median home price: $159,900
Sperling says Birmingham has the highest level of cold-medication use of any city studied, "and allergens were in the 88th percentile -- perhaps as a result of its mild and moist climate."

On the plus side, the 1.2-million-population metro area has only moderate levels of air pollution and flu cases.

Alabama's largest city, Birmingham is home to two large banks, Regions Financial ( RF - Get Report) and BBVA Compass, a unit of Spanish financial giant BBVA ( BBVA)

It also hosts Protective Life ( PL) and other insurance firms, as well as the University of Alabama at Birmingham.

Birmingham's median home prices on rose 0.88% during 2011 to hit $159,900.

There are some 9,900 Greater Birmingham properties listed on the site, with prices ranging from $1,900 for a two-bedroom tear-down to $17.9 million for a 27-acre, 15-bedroom estate in the upscale Shoal Creek neighborhood.

Worst: Oklahoma City, Okla.
Median home price: $149,900
Oklahoma City ranks No. 1 in nasal congestion because of its worst-in-the-nation score for allergens and flu incidence.

Oklahoma's capital city also places in the 85th percentile for smoking and 70th percentile for use of cold-and-flu medicines.

Sperling says the city does have one of the lowest levels of ozone pollution of any area studied.

The largest community in the state, the Oklahoma City metro area has some 1.3 million people.

With an economy heavily focused on oil-and-gas production, the city counts publicly traded Devon Energy ( DVN - Get Report) and Chesapeake Energy ( CHK - Get Report) among local firms.

Oklahoma City is also home to the Sonic ( SONC) fast-food chain and the nearby University of Oklahoma, University of Central Oklahoma and Tinker Air Force Base. lists some 7,500 Oklahoma City-area homes for sale, from an $8,000 two-bedroom fixer-upper to a $4.5 million 15-acre estate in nearby Edmond.

Median home prices rose 3.38% during 2011 to hit $149,900, according to the site.

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