What are the factors affecting asthma susceptibility?

Genetics (development of disease) and environment (onset of symptoms) but complex (all interact with each others) Host factors : genes of atopy and hyperresponsiveness of airway Environmental: indoor dust, furred animal, cockroaches, fung. outdoor: pollen, molds... infectious: viral (RSV increases it 4 folds), occupational , tobacco/pollution.. Allergies: strongest risk factor of asthma (increases 3 folds) Hygiene hypothesis: caused increased allergies (no desensitisation due to increased hygiene)