In this study, our results suggest a population attributable fraction for betel chewing on asthma of 11.7% for males and 1.2% for females, and our findings strongly implicate a relationship between arecoline levels and eotaxin-1 concentrations, providing further evidence for a major role for eotaxin-1 in linking betel chewing with asthma. The gene discussed is CCL11; the disease is asthma.