• by Sarah Mahoney  @mahoney_sarah, March 11, 2011

Sam's Club is upping the ante for retail-based health clinics, offering a one-day free allergy screening effort -- a $500 value -- in select locations.

While many chains often offer free screenings for blood pressure, diabetes, and vision, the Sam's Club allergy test is more extensive, screening for allergic reactions to house and dust mites, cat, timothy grass, Bermuda grass, Mountain Cedar, short ragweed, Alternaria (mold), milk, egg white and wheat. All participants will then receive a personalized plan, called MyAllergyPlan, making suggestions for treatment.

Among its suggestions? Allegra, an allergy medication which just became available without a prescription last week. In fact, the OTC version of Allegra, made by Sanofi-Aventis, is expected to be the big news this allergy season, with Drugstore News, a trade publication, predicting that it may add $100 million to OTC allergy category this year. Walgreens, for example, has been promoting the product on its main site. (A Walgreens spokesperson says it currently has no plans to offer allergy screenings at its clinics.)

In any given year, allergies represent a major marketing opportunity: Some 40 million people suffer from seasonal allergies, according to the Asthma and Allergy Foundation of America, which account for more than half of the 17 million annual allergy outpatient visits.

But this year, allergy season is expected to bring more misery -- and it may be a permanent change. The U.S. Department of Agriculture, in a study that tracked pollen over a 15-year period, reports that global climate change is lengthening the sneezing season. Researchers found that from 1995 to 2009, the number of frost-free days at higher-latitude locations increased, as did the length of the ragweed pollen season. Pollen season lasted from 13 to 27 days longer than in 1995.