Effect of evaporative coolers on skin test reactivity to dust mites and molds in a desert environment

Dust mites and molds are usually not found in arid environments and have a lower prevalence in desert areas. Evaporative (swamp) coolers increase indoor humidity significantly. The purpose of this study is to determine whether evaporative coolers affect the skin test rate to dust mites and molds in patients. Patients with asthma or allergic rhinitis who were undergoing skin testing for molds, indoor allergens, grasses, weeds, and trees were asked about presence of central, window, and evaporative cooler air conditioning in their home. All were tested using the prick technique with controls. One hundred ninety patients between 1 and 42 years (mean, 5.4 years) were evaluated. Fifty-nine (31%) had an evaporative cooler in their home. Twenty-five (42%) of those with evaporative coolers had a positive skin test to at least one mold compared with 26 (19%) without coolers (chi-square, 10.5; p = 0.001). Twenty (34%) of those with evaporative coolers had a positive skin test to dust mites compared with 23 (17.5%) without coolers (chi-square, 6.2; p = 0.013). Children ≤6 years of age had the greatest skin test prevalence (chi-square, 4.3; p = 0.03). In the desert, children in homes using evaporative coolers are significantly more likely to have positive skin tests to molds or mites. This appears to be because of humidity caused by these devices. Patients with asthma in homes with evaporative coolers should be counseled about the risk for mold and dust-mite allergy. Humidity monitoring, cooler maintenance, and filter changes should be discussed.