Occupational Asthma

Asthma can start or get worse because of exposure to allergens or other agents at work.1 This type of asthma is called occupational asthma. The symptoms of occupational asthma are the same as other types of asthma: cough, wheeze, chest tightness, and shortness of breath.2 However, the symptoms usually follow a pattern related to the work schedule. They may start at the beginning or end of a shift, and they improve on the weekend and holidays.

Statistics on occupational asthma

About 9% to 25% of adult asthma cases are work-related.3,4 In the US, occupational asthma is4:

  • More common in women (10.3%) than men (6.3%)
  • More common in black people (9.8%), persons of “other races” (8.8%), and white people (8.7%) than Hispanics (6.3%)
  • Less common in people age 65+ (7.6%) than people under 64 (8.6%)

People who have other allergic diseases, such as eczema, hay fever (allergic rhinitis), or food and drug allergies, are prone to occupational asthma.2

Two similar terms with slightly different meanings are “occupational asthma” and “work-exacerbated asthma.”3 Occupational asthma is asthma caused by the work environment. Work-exacerbated asthma occurs when existing asthma gets worse in the work environment. Occupational asthma includes both of these conditions.

What causes occupational asthma?

The trigger for occupational asthma is also called a sensitizing agent or allergen. A sensitizing agent is typically something a worker is exposed to regularly.1 The sensitizing agent activates the immune system and an allergy develops.5 In other cases of occupational asthma, chemical irritants can damage the lining of the airways and cause asthma symptoms. Irritant-induced asthma has not been studied as well as sensitizer-induced asthma. Ongoing, low level exposure to irritants or single, massive exposures (such as a spill) can cause irritant-induced asthma.

The sensitizing agents that cause the majority of occupational asthma are listed in the Table.2

Table. Major Sensitizing Agents

Flour mills, baking
Cereals, flour, enzymes
Health care workers
Latex, enzymes, biocides, acrylates
Laboratory workers, farmers, seafood processing
Food industry
Enzymes, reactive dyes
Plastics industry, insulation, molding
Metal refinery, welding, electroplating, welding
Adhesives, printing inks, paints and coatings
Beauty technicians
Hair bleacing, hair dyes, acrylates
Epoxy resin workers
Acid anhydride
Reactive Days
Sawmill workers, carpenters
Wood dust

How is it diagnosed?

The first step is to diagnose asthma, and the second step is to connect it to the work environment.3

If your asthma symptoms started or got worse in adulthood, talk with your health care provider about occupational asthma.3 Your provider will probably want to know about:

  • Changes in work processes just before the symptoms started
  • Unusual chemical or allergen exposures in the 24 hours before your symptoms started
  • Changes in your asthma symptoms on weekends, holidays, and vacations
  • Other symptoms such as runny nose or watery eyes that get worse at work

Your provider will probably ask questions about your3:

  • Work history
  • Job duties
  • Exposure to sensitizing agents
  • Use of protective devices or equipment
  • Coworkers’ health

Finally, your provider may recommend some tests to confirm that your asthma is work related.

Peak expiratory flow

Your health care provider may ask you to measure your peak expiratory flow during work and away from work. Peak expiratory flow is the amount of air that comes out of your lungs. This measurement is done using a peak flow meter, which is a portable device. You may be asked to measure your peak flow four times a day for two weeks at work and one to two weeks off work.3,6


Your health care provider may want to perform a methacholine challenge. This test measures how sensitive your airways are, which helps to confirm the diagnosis of asthma. You might be asked to do this test twice: during a work period and during a time away from work.3

Immunologic tests

Your health care provider may recommend skin prick tests or blood work. These tests are done to check for a reaction to certain work allergens.3

Specific inhalation challenge

This test is considered the best way to diagnose occupational asthma.3 It involves exposing a person to the sensitizing agent in a safe, controlled way. However, very few places can perform this test and it is very expensive. Therefore, this test is not used often.

How is occupational asthma treated?

For someone with occupational asthma, avoiding the sensitizing or irritating agent is the best solution.3 People who continue to be exposed have worse symptoms and need more medications.

Unfortunately, it is not always possible to change duties or jobs. In this case, health care providers may recommend asthma medications. The first medications typically recommended are anti-inflammatory medications and a bronchodilator.3

In a few situations, allergy shots may be recommended. Criteria are:

  • A specific, known allergen is causing asthma symptoms.
  • It is impossible to avoid this allergen.
  • An allergen extract is available to be used as treatment.

Examples of successful use of allergy shots are beekeepers who are allergic to insect stings, bakers who are allergic to flour, and veterinarians who are allergic to cats.3

How can occupational asthma be prevented?

When one worker is diagnosed with occupational asthma, this is an opportunity to protect the health of coworkers.

It is ideal to prevent exposure to sensitizing agents before an allergy develops.5 For example, nitrile gloves can be used in place of natural rubber latex. Containing known allergens, improving ventilation, and providing personal protective equipment can reduce exposure. Once occupational asthma develops, early detection and removal of the worker from the exposure may be helpful. However, as many as 70% of people continue to have asthma and airway symptoms for years after leaving the job.5

Reducing exposure to irritating chemicals may allow workers with irritant-induced asthma to stay on the job. This can be done through better ventilation, using a respirator, or enclosing the source of the irritant.3

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Written by: Sarah O'Brien | Last Reviewed: May 2016.