Indoor environmental quality is suspected to be at least part of the cause of the increasing prevalence of childhood asthma and allergy. This study is part of the China, Children, Homes, Health (CCHH) project, which was designed to identify the risk factors indoors that are associated with prevalence of asthma and allergy among children in China. A cross-sectional questionnaire study was carried out in Wuhan in 2011. The questionnaire was a modified (to Chinese building characteristics) version of a questionnaire used first in Sweden. The paren...