Occupational asthma often goes unrecognised.

Occupational asthma is induced de novo by an airborne agent encountered in the workplace. The risk of occupational asthma is greater in those with a prior atopic history. Work-exacerbated asthma is the provocation of pre-existing, or coincidental, disease by one or more irritant exposures at work. Distinguishing occupational from work-exacerbated asthma can be difficult but it is important since the two have very different clinical, occupational and legal implications. Occupational asthma is underrecognised, the disease often develops in young people who are otherwise fit. They may not recognise their symptoms as anything out of the ordinary, or may confuse them with hay fever or a cold. It is sensible to consider occupational and work-exacerbated asthma in every working adult who has asthma or who presents with suggestive symptoms such as rhinitis. Occupational asthma almost always arises from an immediate-type hypersensitivity reaction to a respiratory sensitising agent in the workplace. The disease has a short latency with symptoms developing 6 to 36 months after employment in a new job. Rhinitis is common and in those working in an environment with airborne proteins the absence of rhinitis effectively rules out occupational asthma. In occupational asthma, symptoms (including nasal symptoms) improve away from work. Once the disease is established symptoms are provoked by even very small exposures at work and begin to be provoked by a wide variety of irritant exposures both at, and away from, work. It is good practice to enquire into the employment of every working-age adult with asthma, or rhinitis, and particularly in those presenting with new symptoms or symptoms that have become more difficult to manage. Patients should routinely be asked whether their symptoms improve when they are not at work.