Relationships Between Secondhand Smoke Incursion and Wheeze, Rhinitis, and Eczema Symptoms in Children Living in Homes Without Smokers in Multi-Unit Housing.

Introduction Secondhand smoke (SHS) incursion can occur in units of multi-unit housing (MUH). The purpose of this study was to determine the relationship between SHS incursion and allergic symptoms in children living in MUH without smokers. Methods We conducted a cross-sectional study from May to September 2015 in Seoul, Korea. Children were recruited from elementary schools, kindergartens, and daycare centers. In total, 16676 children between 1 and 13 years of age living in MUH without smokers were included in the analysis. Allergic symptoms during the previous 12 months (current wheeze, rhinitis, and eczema) and home environmental factors, including the frequency of SHS incursion during the previous 12 months, were examined using a questionnaire filled out by the parents or guardians of the children. Results The prevalence of current allergic symptoms in children was 4.9% for wheeze, 42.0% for rhinitis, and 28.1% for eczema. The prevalence of SHS incursion into the children's homes was 61.6%. In a multivariable logistic regression analysis adjusted for demographic and home environmental factors, children living in homes with SHS incursion (either no more than once a month or more than once a month) were more likely to have current wheeze, rhinitis, and eczema than those with no SHS incursion. Conclusions More than half of the children's homes in MUH without smokers had SHS incursion. SHS incursion into homes was associated with wheeze, rhinitis, and eczema symptoms in children. Implications Children living in multi-unit housing (MUH) can be exposed to secondhand smoke (SHS) from smoke transferred from neighboring units with smokers. This study found that more than half of the children's homes without smokers in MUH had SHS incursion. Children living in homes with SHS incursion (either no more than once a month or more than once a month) were more likely to have current wheeze, rhinitis, and eczema than those with no SHS incursion. We confirmed that SHS incursion was associated with allergic symptoms in children.