What is hypersensitivity pneumonitis?
Hypersensitivity pneumonitis is a disease in which the air sacs of the lungs become inflamed when a person breathes in certain dusts they are allergic to. Farmer’s lung is the best known type of this disease, as it is caused by molds that grow on hay, straw, or grains. Often this disease is named for the type of job where theses molds have been from, such as mushroom-worker’s lung or chicken plucker's lung.
When a person inhales these dusts the first time, no problem is seen, but after frequent exposure to the dust some people may start to have symptoms. The tiny air sacs in the lungs become inflamed, fill up with white blood cells, and sometimes fill with fluid. Over time, parts of the lung may get scar tissue and can no longer function well for breathing.
What are the symptoms?
The symptoms of an acute attack are like the flu and appear 4-6 hours after the person breathes the dust. These symptoms may include:
- Dry cough
- Shortness of breath
- Tight feeling in the chest
The symptoms may last for as little as 12 hours or as long as 10 days. Between attacks the person may have no symptoms and feel normal.
After prolonged exposure to the dust, chronic cough with a lot of sputum and pus may occur. Over time, there may be chronic shortness of breath. The person may also show a lack of hunger and weight loss.
Who gets hypersensitivity pneumonitis?
Hypersensitivity pneumonitis occurs most often in people exposed to certain dusts in their work or living, such as dusts that contain fungus spores from mold. Only about 5 to 20% of the people who are exposed will get this disease. The chance of getting this disease is higher when there is frequent breathing of large amounts of these dusts.
What causes hypersensitivity pneumonitis?
It is caused by mold that grows on hay, straw, or grains, and by other things found on farms. Also dusts from moldy sugar cane and barley, maple bark, cork, animal hair, bird feathers and droppings, mushroom compost, coffee beans, and paprika can cause this.
How is it diagnosed?
A careful history, blood tests and finding molds from the workplace may help. Chest x-rays, CT scans, and breathing tests may show effects of the disease during sudden attacks or in the chronic stage of the disease. These tests may then be normal between these attacks when the patient has no symptoms. Sometimes, testing a very tiny piece of lung tissue (lung biopsy) is needed to tell this disease apart from other lung problems.
Can it be prevented?
The mold that causes farmer’s lung grows only in moisture, so proper drying and storage of farm products can help avoid this. Good air flow in the work place and using masks can also help prevent this.
If a worker starts to have symptoms, the process can be stopped if it is found early. If control measures do not work or can not be done, it may be best to change jobs.
What is the treatment?
The single most vital step is to avoid the dust. Steroids can relieve the symptoms of acute attacks, but do not cure the disease. Getting over acute attacks may take as long as three weeks. Lung damage may become long term and may occur even after the symptoms have gone away.
Does smoking affect hypersensitivity pneumonitis?
We do not know that smoking helps cause this, but it may make symptoms worse. Smokers are likely to get other lung disease such as emphysema, chronic bronchitis, or lung cancer.
For more information, see the American Lung Association website, www.lungusa.org or call them at 1-800-LUNG-USA (1-800-586-4872).
The information provided should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Any duplication or distribution of the information contained herein is strictly prohibited.
Last Updated: 02/01/2010
Copyright © 02/01/2010 University of Wisconsin Hospitals and Clinics Authority. All rights reserved. Produced by the Department of Nursing. HF#6502
Print Health Fact For You