Asthma is the most common chronic disease in children. It affects eight to 10 per cent of the population in developed countries, and rates are increasing. Susceptibility to asthma and other allergic diseases runs in families, which indicates that genes influence its development. However, numerous studies examining the influence of changes in the genetic code have led to inconsistent results. A possible explanation for the inconsistency is a failure to account for epigenetics. This emerging field of study involves investigating the basis of inherited traits that affect how genes function without affecting the sequence of the underlying genetic code. The airway lining cells, or epithelium, are a promising cell type in which to identify novel mechanisms of asthma. Jian-Qing He is studying cultured airway epithelial cells from 150 asthmatic and non-asthmatic children to explore whether a combination of genetic and epigenetic changes in immunity-related genes are central to the development of childhood asthma. Results from this study will allow for a better understanding of how genetic and epigenetic differences in epithelial cells are related to the development of asthma. Potentially, such knowledge could contribute to the development of more effective methods of screening for susceptibility to asthma and better preventive strategies.