Diagnosing Work-related Asthma
At a glance
Diagnosing work-related asthma is based on a combination of medical and exposure history, physical examination, and medical tests such as pulmonary function tests.
Considerations
Consider work-related asthma as a possibility in all working patients. This includes those with new onset asthma or asthma that clinically worsens after previously being controlled.
Ask patients screening questions about their working conditions. If their answers suggest a connection, obtain a comprehensive work history. The work history should include:
Current and past job titles Job descriptions Known exposure
Examples of work history questions
What kind of work do you do? Are you now or have you previously been exposed to dust, fumes, or chemicals at your workplace? Are your respiratory symptoms better or worse when away from work, such as on weekends or vacation?
Do you think your health problems are related to your work?
An electronic occupational exposure history form is available at the Agency for Toxic Substances and Disease Registry (ATSDR) website .
Evaluate symptoms and work schedules
Symptoms can occur at work in response to an exposure or can be delayed (occurring several hours after work). Symptoms of severe work-related asthma might not improve away from work for a work-related pattern to be evident.
Document changes in medication
An increase in using rescue inhalers can be an early indication that asthma is progressing.
Physical examination
Exam findings are typically non-specific. Patients with asthma often have normal physical examinations between asthma attacks. If wheezing is present, it is generally on expiration.
However, sometimes wheezing might also be auscultated on inspiration.
Temporary work furlough
A short period away from work period can help diagnose patients you suspect have work-related asthma. When away, improvements in pulmonary function tests such as ambulatory peak expiratory flow or bronchial responsiveness measured by methacholine challenge support an occupational etiology.
Differential diagnosis
Some health conditions have symptoms similar to asthma. In adults, the differential diagnosis of asthma includes, but is not limited to, the following:
Chronic obstructive pulmonary disease (COPD) Non-asthmatic eosinophilic bronchitis Hypersensitivity pneumonitis Vocal cord dysfunction Obliterative bronchiolitis
Medical tests
Pulmonary function tests
The American Thoracic Society has guidelines on how to perform and interpret pulmonary function tests such as spirometry.
Peak expiratory flow
Serial measurements of peak expiratory flow might be useful for evaluating work-related asthma. Provide instructions to the patient on how to use a peak flow meter (spirometer). Ask the patient to record their peak expiratory flow:
Four times a day on when off work On workdays (before, during and after work) Before going to bed every day
Record measurements in a journal or diary over several weeks for best interpretations. Many spirometers automatically record measurements with date and time information. This can be downloaded from a clinical office for review.
Bronchodilator reversibility testing for spirometry
When spirometry results show a patient has airways obstruction, the next step is to assess reversibility with an inhaled bronchodilator. The presence of reversibility may support an asthma diagnosis.
Nonspecific bronchial responsiveness (bronchoprovocation testing)
If spirometry is normal but asthma is suspected, bronchial hyperresponsiveness can be assessed using nonspecific bronchial responsive testing (e.g., methacholine or mannitol challenge tests).
Exhaled nitric oxide
Fractional exhaled nitric oxide is a marker of allergic airways inflammation. The American Thoracic Society has guidelines on how to measure and interpret exhaled nitric oxide levels. Increased fractional exhaled nitric oxide levels support allergic asthma diagnosis but does not differentiate between work-related asthma and non-work related.
A normal fractional exhaled nitric oxide level does not rule out work-related asthma.
Other tests
Serologic testing to measure IgE antibodies for specific allergens. Skin prick, patch, or intradermal testing to look for allergic reactions to specific substances.
Some medical conditions can make asthma worse. Additionally, other tests are needed to evaluate for gastroesophogeal reflux and rhinosinusitis.
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Oct. 28, 2026 Sources and Page Info Print Share
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National Institute for Occupational Safety and Health About This Page
Published: May 15, 2024
Updated: October 28, 2026 This page was last updated on this date. Updates may include minor edits, image changes, or other modifications to page content.
Reviewed: February 25, 2025 The information on this page was last reviewed by subject matter experts to ensure accuracy.
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