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Occupational asthma

Definition

Occupational asthma is a lung disorder in which substances found in the workplace cause the airways of the lungs to swell and narrow, leading to attacks of wheezing, shortness of breath, chest tightness, and coughing.

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Alternative Names

Asthma - occupational exposure; Irritant-induced reactive airways disease

Causes, incidence, and risk factors

Many substances in the workplace can cause occupational asthma. The most common triggers are wood dust, grain dust, animal dander, fungi, or other chemicals (especially diisocyanates).

Though the actual rate of occurrence of occupational asthma is unknown, it is suspected to cause 2 - 20% of all asthma cases in industrialized nations.

The following workers are at higher risk:

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

Symptoms

Symptoms are usually due to swelling of the airways and spasms of the muscles lining the airways. This reduces the amount of air that can pass through, and can lead to wheezing sounds. See also: Asthma

Symptoms usually occur shortly after you are exposed to the substance, and often improve or go away when you leave work. Some people may not have symptoms until 12 or more hours after being exposed to the allergen.

Symptoms usually get worse toward the end of the work week and may (but not always) go away on weekends or vacations.

In general, symptoms include:

Coughing
Tight feeling in the chest
Shortness of breath
Wheezing

Signs and tests

The health care provider will perform a physical exam and ask questions about your medical history. Your symptoms may have a pattern of getting worse with a certain workplace environment or substance.

The health care provider may hear wheezing when listening to the chest with a stethoscope.

The following tests may be used to diagnose this condition:

Blood tests to look for antibodies to the substance
Bronchial provocation test (test measuring reaction to the suspected allergen)
Chest x-ray
Complete blood count
Peak expiratory flow rate
Pulmonary function tests

Treatment

Avoiding exposure to the substance that is causing your asthma is the best treatment.

The best option is to change jobs, but this may be difficult to do.
Moving to a different location at the job where there is less exposure to the substance may help, but it does not seem to make a difference for many people. Over time, even a very small amount of the substance can trigger an asthma attack.
Using a respiratory device to protect or reduce your exposure may help.

Asthma medicines (almost always inhalers) may help you manage your symptoms. Talk to your doctor about these medicines.

Asthma quick-relief drugs help relax the muscles of your airways. They are called bronchodilators.
Asthma control drugs are taken every day to prevent symptoms.

Support Groups

See: Asthma and allergy - support group

Expectations (prognosis)

Occupational asthma may keep getting worse if you continue to be exposed to the substance that is causing the problem, even if medicines improve your symptoms. You may need to change jobs.

Sometimes, symptoms may continue even when the substance is removed.

In general, the outcome for people with asthma is good. However, symptoms may continue for years after you are no longer exposed in the workplace.

Calling your health care provider

Call your health care provider if you have symptoms of asthma.

References

Chan-Yeung M, Malo JL. Asthma in the workplace and occupational asthma. In: Mason RJ, Broaddus VC, Martin TR, et al. Murray & Nadel's Textbook of Respiratory Medicine. 5th ed. Philadelphia, Pa: Saunders Elsevier; 2010:chap 64.

Cowl CT. Occupational asthma: review of assessment, treatment, and compensation. Chest. 2011;139(3):674-681.

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