There are many agents in the workplace that can cause occupational asthma. Most commonly, these include protein molecules (wood dust, grain dust, animal dander, fungi) or other chemicals (especially di-isocyanates). Though the actual rate of occurrence of occupational asthma is unknown, it is suspected to cause between 2 and 20 percent of all cases of asthma in industrialized nations.

The following workers are at higher risk:

• Plastics workers
• Metal workers
• Bakers
• Millers
• Farmers
• Grain elevator workers
• Laboratory workers
• Woodworkers
• Drug manufacturers
• Detergent manufacturers

Symptoms usually occur shortly after exposure to the offending agent (the allergen) and often improve or disappear when the affected person leaves the workplace. The symptoms often worsen as the work week progresses and resolve on weekends or vacations. Some people may experience a delayed onset of symptoms, occurring as many as 12 hours after exposure to the allergen.

• Shortness of breath
• Wheezing
• Cough
• A feeling of tightness in the chest

The history reveals a pattern of worsening symptoms associated with exposure to a specific agent or workplace environment. Making the association with the correct allergen can be very difficult.

Wheezing may be heard when listening to the chest with a stethoscope (auscultation).

Tests used in the diagnosis of occupational asthma may include the following:

• Pulmonary function tests
• Measurement of the peak expiratory flow rate (peak-flow) before and after work
• Chest X-ray
• CBC
• Bronchial provocation test (test measuring reaction to the suspected allergen)
• Blood tests to reveal specific antibodies to suspected offending substances