[Etiological factors of asthma and their relation with bronchial hyperreactivity].

As asthma is nearly always associated with non-specific bronchial hyperreactivity, this factor has been considered to be an essential requirement for the development of symptomatic asthma. Some factors appear to be inducers of bronchial hyperreactivity and others promotors of asthmatic symptoms. In clinical practice, it is very difficult to classify aetiological factors as inducers or promotors: there is evidence to support the fact that the same factors may cause both bronchial hyperreactivity and asthmatic symptoms; conversely, the evidence for hereditary non-specific bronchial hyperreactivity is hardly convincing. These observations suggest that non- specific bronchial hyperreactivity is more a marker of bronchial asthma than a true aetiological factor.