Byssinosis - work-aggravated asthma

Alternative names
Asthma - occupational exposure; Occupational asthma; Irritant-induced reactive airways disease

A lung disorder characterized by attacks of breathing difficulty, wheezing, prolonged exhalation, and cough, which is caused by various agents found in the work place (see also bronchial asthma). These symptoms are usually due to spasms of the muscles lining the airways, which cause them to narrow excessively.

Causes, incidence, and risk factors

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

Signs and tests

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

The objective of treatment is to limit exposure to the allergen and improve symptoms with bronchodilator therapy. In some instances, symptoms may persist despite removal of the source of exposure. Medications include hand-held inhalers or nebulizers to deliver bronchodilators. Other therapies for bronchial asthma may be added in more severe cases.

Support Groups
The stress related to illness can often be helped by joining a support group where members share common experiences and problems. See asthma and allergy - support group.

Expectations (prognosis)
The outcome for people with asthma in general is good, but symptoms may persist for years after workplace exposure has been eliminated.

Complications include continued asthma symptoms after removal from the source of exposure.

Calling your health care provider
Call your health care provider if signs of occupational asthma develop.

Call your health care provider if you have occupational asthma and signs of respiratory infection, or if other new symptoms, develop.

Once the cause is determined, avoid further exposure to it.

Johns Hopkins patient information

Last revised: December 6, 2012
by Simon D. Mitin, M.D.

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.