Definition and diagnosis of occupational asthma.

Asthma is the most frequent occupational lung disease. The diagnosis of occupational asthma, defined as variable airways narrowing, causally related to exposure in the working environment to specific airborne dusts, gases, vapours or fumes, needs to be confirmed by objective means. This article reviews the different steps of investigation which are: history, pulmonary function tests, immunological tests, monitoring of peak expiratory flows and nonallergic bronchial responsiveness and, finally, the gold standard, specific bronchial provocation.