How does cigarette smoke cause asthma?

In the same way as any other trigger. However, there is a widely held theory that it is not so much the trigger which causes most attacks but the stress arising from the PERCEPTION that any exposure to that trigger will cause an attack. In other Words, it's psychological. Tobacco Control have created the PERCEPTION that tobacco smoke is more dangerous than cyanide. One whiff and it's an instant Asthma attack, or even worse a heart attack! Smoking prevalence has fallen significantly over the last few decades yet the incidence of asthma has rocketed. Work that one out!