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.
May. 19, 2011