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Causes
By Mayo Clinic staffIt's not clear why some people develop occupational asthma from exposure to something at work and others don't. 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 sulfur dioxide, chlorine, hydrochloric acid and environmental smoke.
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, flour conditioners, some pharmaceuticals and meat tenderizers.
- 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.
- Chan-Yeung M. Overview of occupational asthma. http://www.uptodate.com/home/index.html. Accessed April 29, 2009.
- Malo J. Diagnosis and clinical assessment of asthma. http://www.uptodate.com/home/index.html. Accessed April 29, 2009.
- Dykewicz MS. Occupational asthma: Current concepts in pathogenesis, diagnosis, and management. Journal of Allergy and Clinical Immunology. 2009;123:519.
- GINA report, global strategy for asthma management and prevention. Cape Town, South Africa: Global Initiative for Asthma. http://www.ginasthma.org/Guidelineitem.asp??l1=2&l2=1&intId=1561. Accessed April 29, 2009.
- Chan-Yeung M. Pathogenesis of occupational asthma. http://www.uptodate.com/home/index.html. Accessed April 29, 2009.
- Tips to Remember: Occupational asthma. American Academy of Allergy, Asthma and Immunology. http://aaaai.org/patients/publicedmat/tips/occupationalasthma.stm. Accessed April 29, 2009.
- Malo J, et al. Occupational asthma. In: Adkinson N, et al: Middleton's Allergy: Principles and Practice. 7th ed. Philadelphia, Pa.: Elsevier. 2009. http://www.mdconsult.com/das/book/body/134488541-3/0/1806/57.html?tocnode=56310176&fromURL=57.html#4-u1.0-B978-0-323-05659-5..00053-X_1739. Accessed April 29, 2009.
- Smith AM, et al. Management of work-related asthma. Journal of Allergy and Clinical Immunology. Journal of Allergy and Clinical Immunology. 2009;123:551.
- Passalacqua G, et al. ARIA update: I - Systematic review of complementary and alternative medicine for rhinitis and asthma. Journal of Allergy and Clinical Immunology. 2006;117:1054.
- Steurer-Stey C. Complementary and alternative medicine in asthma: Do they work? Swiss Medicine Weekly. 2002;132:338.
- Hayes M, et al. Are any alternative therapies effective in treating asthma? The Journal of Family Practice. 2007;56:385.
- Horwitz R. Controlling asthma: The role of nutrition. Explore Journal of Science and Healing. 2005;5:393.
- Mainardi T, et al. Complementary and alternative medicine: Herbs, phytochemicals and vitamins and their immunologic effects. Journal of Allergy Clinical Immunology. 2009;123:283.
