Moldy odor from air conditioners in the residences of Japanese participants with and without asthma.

Fungi, a major allergen associated with asthma onset and severity, can contaminate air conditioners if not properly maintained. We surveyed the prevalence and risk factors associated with fungal contamination of air conditioners and patient behavior to reduce this contamination. Japanese adults aged ≥30 years registered in the database of an Internet research company were asked to participate in an online survey. A moldy odor from the air conditioners in their residences was used as an indicator of fungal contamination. Among a total of 1006 adults, including 631 patients with asthma, 37.1% reported a moldy odor from air conditioners. The prevalence was higher in residences with indoor condensation and in air conditioners used for ≥6 years or frequently during the summer, but was lower in air conditioners with an auto-cleaning function. The risk of indoor condensation was higher in apartments, in the presence of an aquarium, and in the absence of a 24-h ventilation system. These risk factors did not differ between the residences or air conditioners of participants with and without asthma. Asthmatic patients were conscious of indoor air quality; however, do not necessarily take appropriate measures to reduce indoor mold contamination, possibly due to a lack of knowledge. In conclusion, appropriate patient education is required to reduce environmental fungal contamination and improve asthma control.