Occupational asthma

Occupational asthma is a hypersensitivity syndrome, and must be distinguished from non-specific aggravation of existing asthma. Probably only a minority of the causal agents produce sensitization by allergic mechanisms. The important clinical features of occupational asthma are the latent period before the onset of symptoms, the characteristic periodicity of symptoms, and the progressive increase in the severity of symptoms with continuing exposure. The diagnosis can usually be made from the history; serial measurements of peak expiratory flow will provide objective confirmation of the diagnosis. Identification of the agent responsible is desirable but not essential to the diagnosis, and specific bronchial challenge with the causal agent should be reserved for atypical cases. Symptomatic or prophylactic drug treatment should never be more than a short-term measure. The most effective treatment is for the patient to change his job.