Case history
Case history #1
A 45-year-old woman has worked for 12 years in a company making polyurethane foam. She works close to the foam production line and her job is to inspect the fresh foam. She has a 3-year history of episodic cough, wheeze, and shortness of breath with chest tightness. She recently noticed that while off work for 6 weeks following knee surgery, her symptoms significantly improved, but again worsened within 2 days of return to work. On questioning she reports slight improvement at the end of weekends off work and that she had also noticed some improvement when on holiday. While working she has been woken at night by her respiratory symptoms and has needed progressively more asthma drugs for her symptoms over the past 3 years. She has no previous history of asthma. Some of her co-workers have also developed similar symptoms.
Case history #2
A 56-year-old man who never smoked and has no previous respiratory symptoms develops acute onset of chest tightness, wheeze, shortness of breath, and dry cough within minutes of accidentally mixing bleach and ammonia in a washroom during his work as a cleaner. He was wearing no respiratory protection.
Other presentations
Sensitiser-induced occupational asthma (OA) can be caused by over 300 known sensitising agents, and new agents continue to be described. Numerous potential respiratory irritant agents, in high concentrations, could cause irritant-induced OA. The absence of a known sensitiser at work does not exclude OA, but the presence should increase suspicion of the diagnosis. The diagnosis of OA should be suspected in any patient with asthma whose asthma begins or worsens while working. An accidental exposure at work shortly before the onset of symptoms increases suspicion of irritant-induced OA. The presence of associated symptoms of allergic rhinitis and/or conjunctivitis that is worse at work increases the probability of a sensitiser-related workplace component to asthma, and may frequently precede the development of asthma. A history of improvement in asthma symptoms when off work, especially when away for a few weeks (e.g., on holiday, or on weekends off) or, less commonly, a few hours after finishing a work shift, increases the probability of sensitiser-induced OA. These features should lead to specific objective investigations. However, occasionally in those with sensitiser-induced OA, an improvement may be seen only after several weeks away from the work exposure, or symptoms may be masked by asthma drugs.
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