This is a multi-center observational study. Asthmatic patients attending major hospitals in Riyadh with clear and well defined inclusion criteria (see below for details, Appendix I) will be recruited. We anticipate recruiting 1000 asthmatic patients and comparable number of control subjects. The controls will be recruited from people attending blood bank for donation or other patients attending different clinics with history excluding atopic diseases and asthma. Ethical approval for this study will be obtained from CMRC ethical committee of the KKUH as well as other involved centers