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Causes

By Mayo Clinic staff

It's not clear why some people develop occupational asthma from exposure to something at work. It likely has to do with inherited traits (genetics) and exposure to environmental substances over time.

Asthma symptoms start when your lungs become irritated (inflamed). Inflammation causes several reactions that restrict the airways, making breathing difficult. After you're exposed to something that triggers an asthma attack, your airways become constricted:

  • Muscles around your airways tighten.
  • The airways themselves become swollen.
  • You begin to produce too much mucus, which clogs your airways.

With occupational asthma, lung inflammation may be triggered by one of two processes:

  • An allergic response. Asthma can occur when the body develops an allergy from continued exposure to a substance. Your body starts to identify the substance as a threat and activates your immune system to react. This is called sensitization. You don't have symptoms at first because the sensitization process can take months or even years to occur. Symptoms start when your immune system begins to produce specific antibodies against the irritating substance. This, in turn, triggers the release of chemicals, such as histamine, which inflame the lungs and cause asthma symptoms.
  • Irritant-induced asthma. After breathing in a certain workplace irritant one or more times, you may develop asthma symptoms caused by direct irritation of your lungs rather than an allergic reaction. With a condition called reactive airways dysfunction syndrome (RADS), inhaled chemicals make the bronchial tubes more sensitive to irritants. Some irritants that can cause this type of reaction include chlorine, hydrogen sulfide, anhydrous ammonia and phosphoric acid.

More than 300 workplace substances have been identified as possible causes of occupational asthma. These substances include:

  • Animal substances, such as proteins found in dander, hair, scales, fur, saliva and body wastes.
  • Chemicals, such as anhydrides, diisocyanates and acids used to make paints, varnishes, adhesives, laminates and soldering resin. Other examples include chemicals used to make insulation, packaging materials, and foam mattresses and upholstery.
  • Enzymes used in detergents and flour conditioners.
  • Metals, particularly platinum, chromium and nickel sulfate.
  • Plant substances, including proteins found in natural rubber latex, flour, cereals, cotton, flax, hemp, rye, wheat and papain, a digestive enzyme derived from papaya.
  • Respiratory irritants, such as chlorine gas, sulfur dioxide and smoke.
Risk factors Symptoms

  • See Also

    • Hand Scheduled
    Section Focus
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  • Asthma attack

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References
  1. Occupational asthma. The Merck Manuals: The Merck Manual for Healthcare Professionals. http://www.merckmanuals.com/professional/sec05/ch057/ch057h.html?qt=occupational%20asthma&alt=sh. Accessed Jan. 28, 2011.
  2. Malo J. Diagnosis and clinical assessment of asthma. http://www.uptodate.com/home/index.html. Accessed Jan. 28, 2011.
  3. Tarlo SM. Occupational exposures and adult asthma. Immunology and Allergy Clinics of North America. 2008;28:563.
  4. Dykewicz MS. Occupational asthma: Current concepts in pathogenesis, diagnosis, and management. Journal of Allergy and Clinical Immunology. 2009;123:519.
  5. Bardana EJ. Occupational asthma. Journal of Allergy and Clinical Immunology. 2008;121:S408.
  6. Maestrelli P, et al. Mechanisms of occupational asthma. Journal of Allergy and Clinical Immunology. 2009;123:531.
  7. Mapp CE, et al. Occupational asthma. American Journal of Respiratory and Critical Care Medicine. 2005;172:280.
  8. Smith AM, et al. Management of work-related asthma. Journal of Allergy and Clinical Immunology. 2009;123:551.
  9. Balkissoon R. Asthma overview. Primary Care: Clinics in Office Practice. 2008;35:41.
  10. Guidelines for the diagnosis and management of asthma. Bethesda, Md.: National Heart, Lung, and Blood Institute. http://www.nhlbi.nih.gov/guidelines/asthma/asthgdln.pdf. Accessed Jan. 28, 2011
  11. Updated information on leukotriene inhibitors: Montelukast (marketed as Singulair), zafirlukast (marketed as Accolate), and zileuton (marketed as Zyflo and Zyflo CR). U.S. Food and Drug Administration. http://www.fda.gov/Drugs/DrugSafety/PostmarketDrugSafetyInformationforPatientsandProviders/DrugSafetyInformationforHeathcareProfessionals/ucm165489.htm. Accessed Feb. 5, 2011.
  12. Kealoha MK. What's new in alternative therapies for asthma in children? Journal of Community Health Nursing. 2009;26:198.
  13. Engler RJ, et al. Complementary and alternative medicine for the allergist-immunologist:Where do I start? Journal of Allergy and Clinical Immunology. 2009;123:309.
  14. Li XM, et al. Efficacy and mechanisms of action of traditional Chinese medicines for treating asthma and allergy. Journal of Allergy and Clinical Immunology. 2009;123:297.
  15. Ernst E. Spinal manipulation for asthma: A systematic review of randomised clinical trials. Respiratory Medicine. 2009;103:1791.
  16. OSHA frequently asked questions. Occupational Safety & Health Administration. http://www.osha.gov/OSHA_FAQs.html. Accessed Feb. 5, 2011.
DS00591 May 19, 2011

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