This year's ranking of Spring Allergy Capitals is in, and it's bad news yet again for allergy sufferers in the Southern half of the United States. Jackson, Mississippi, and Louisville, Kentucky, top the 2015 list of the "most challenging places to live with allergies," published annually by the Asthma and Allergy Foundation of America. Oklahoma City, Memphis, and Knoxville round out the top five.
What makes these cities especially allergenic? Each has its own unique cocktail of airborne allergens, of course. Tree pollen is a major culprit in seasonal allergies, and certain types of trees, such as mulberry and olive, are more allergenic than others. There are also factors that tend to exacerbate symptoms across the board. Air pollution is believed to intensify allergic responses, and geography can compound the effect; Louisville, for instance, tends to trap allergens because of its location in the Ohio River Valley. Climate change also plays a role: increases in temperature, carbon dioxide, and precipitation stimulate the growth of some allergenic species and lengthen pollination periods.