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Alveolitis, Extrinsic Allergic

Synonyms of Alveolitis, Extrinsic Allergic

  • Allergic Interstitial Pneumonitis
  • Extrinsic Allergic Pneumonia
  • Hypersensitivity Pneumonitis

Disorder Subdivisions

  • No subdivisions found.

General Discussion

Extrinsic allergic alveolitis is a lung disorder resulting from repeated inhalation of organic dust, usually in a specific occupational setting. In the acute form, respiratory symptoms and fever begin several hours after exposure to the dust. The chronic form is characterized by gradual changes in the lung tissue associated with several years of exposure to the irritant.


In general, symptoms of all forms of Extrinsic Allergic Alveolitis include breathing difficulty, wheezing, and dry coughs that appear to shake the entire body. Chills, sweating, aching, discomfort and/or fatigue may accompany lung symptoms. Most cases of this disorder are characterized by mild, short episodes that may be misdiagnosed. Chronic cases may develop with repeated episodes or prolonged exposure to a specific organic dust. These may involve more severe symptoms including fever, crackling sounds during breathing (rales), breathing difficulty, bluish appearance of the skin (cyanosis), and possibly, expectoration of blood 3.


Extrinsic allergic alveolitis is caused by repeated exposure to animal or vegetable dusts, usually but not exclusively, in occupational settings. In order to get into the lung's tiny sacs where the oxygen is exchanged with the blood, these dusts must be less than a certain size, described as 5 microns. (A micron is one-millionth of a meter in size, and thus about one twenty-five thousandth of an inch.)

A wide variety of substances encountered in occupational settings may be linked to this disorder, including irritants associated with birds (avian dust), cheese manufacturing (mold), sugar manufacturing (moldy sugar cane dust), bath tub refinishing (paint catalyst), farming (moldy hay dust), mushroom farming (mushroom compost), working in a laboratory (rat or gerbil urine residue), tobacco (snuff), heating and cooling systems (moldy water), malt working/beer brewing (moldy barley), maple bark disease (moldy maple bark dust), sequoiosis (moldy redwood bark dust), suberosis (moldy cork dust), plastic working (plastic residue), epoxy resin (heated epoxy residue), enzyme detergent (dust), or wheat weevil disease (wheat mold or dust).

Affected Populations

Extrinsic allergic alveolitis may affect males and females in equal numbers, but usually affects individuals in occupations in which animal or vegetable dusts are inhaled by people allergic to the substances contained in such dusts.

Related Disorders

Symptoms of the following disorders can be similar to extrinsic allergic alveolitis. Comparisons may be useful for a differential diagnosis:

Asthma is characterized by breathing difficulty caused by a wide variety of factors, often associated with allergies. In general, the air passages become narrowed and may return to normal spontaneously, although treatment is often necessary. Long-term cases can diminish in severity, depending on the underlying cause and method of treatment. There is no known cure, but attacks may be controlled to various degrees.

Desquamative interstitial pneumonia is a chronic form of pneumonia. The exact cause of this disorder is not known. Symptoms are caused by shedding of large alveolar cells (desquamation) in the lungs and thickening of the walls of the air passages. This disorder is characterized by breathing difficulty and accompanied by a harsh cough that does not seem to clear the obstruction.

Fibrosing alveolitis, also known as acute pulmonary alveolitis, is an inflammatory lung disorder characterized by abnormal formation of fibrous tissue between tiny air sacs (alveoli) or ducts in the lungs. Coughing and rapid, shallow breathing may develop even with moderate exercise. The skin may become bluish (cyanotic) due to lack of oxygen circulating in the blood. Complications such as infections, emphysema or heart problems may develop. (For more information on this disorder, choose "Fibrosing Alveolitis" as your search term in the Rare Disease Database.)

Granulomatous pneumonitis is a rare lung disease characterized by inflamed nodules in the lungs. Inhalation of various antigens, such as bacteria (even dead bacteria), or microbial cell fragments may overstimulate the immune system in the lungs leading to disease symptoms. An antigen is a substance, usually protein or carbohydrate, that is capable of stimulating an immune response. With respect to granulomatous pneumonitis, it is the immune response that causes the syndrome. Symptoms include lung complications, dry cough, and shortness of breath. This respiratory problem is often misdiagnosed as tuberculosis or some other lung disease.

Sarcoidosis is a disorder that affects many body systems. It is characterized by small round lesions (tubercles) in tissue. Symptoms may vary depending on the severity of the disease and the proportion of the body that is affected. Widespread lung involvement may occur with or follow lymph node involvement. This infiltration may have a fine "ground-glass" appearance on X-rays, and may appear to have an unusual pattern, or resemble tumors. Lung involvement is usually characterized by coughing and breathing difficulty, although these symptoms can be mild or even absent. (For more information on this disorder, choose "Sarcoidosis" as your search term in the Rare Disease Database.)

Standard Therapies

Treatment of extrinsic allergic alveolitis initially depends on identification of the cause of the allergic reaction. If possible, the patient should avoid exposure to the allergen. In an occupational setting, mild cases may be alleviated by improved ventilation or use of air filtering masks. In severe or prolonged cases, however, changing jobs may be the better option. If symptoms persist in spite of avoidance, corticosteroid drugs may be tried. In acute cases, steroids in combination with avoidance measures can often reduce the severity of symptoms. All symptoms can usually be resolved in acute cases if they are diagnosed and treated early before permanent changes in the lungs can develop. If permanent lung changes have occurred at the time of diagnosis, it is possible that the patient may not respond well to treatment.

Investigational Therapies

Information on current clinical trials is posted on the Internet at All studies receiving U.S. government funding, and some supported by private industry, are posted on this government website.

For information about clinical trials being conducted at the National Institutes of Health (NIH) in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222
TTY: (866) 411-1010

For information about clinical trials sponsored by private sources, contact:

Alveolitis, Extrinsic Allergic Resources



Moore JE, Convery RP, Millar BC, et al. Hypersensitivity pneumonitis associated with mushroom worker's lung: an update on the clinical significance of the importation of exotic mushroom varieties. Int Arch Allergy Immunol. 2005;136:98-102.

Story RE, Grammer LC. Hypersensitivity pneumonitis. Allergy Asthma Proc. 2004;25(4 suppl 1)S40-41.

Miranowski AC, Grammer LC. Occupational immunologic lung disease. Allergy Asthma Proc. 2004;25(4 suppl 1)S36-37.

Greenberger PA. Mold-induced hypersensitivity pneumonitis. Allergy Asthma Proc. 2004;25:219-23.

Selman M. Hypersensitivity pneumonitis: a multi-faceted deceiving disorder. Clin Chest Med. 2004;25531-47.

Mohr LC. Hypersensitivity pneumonitis. Curr Opin Pulm Med. 2004;10:401-11.

Agostini C, Trentin L, Facco M, et al. New aspects of hypersensitivity pneumonitis. Curr Opin Pulm Med. 2004;10:378-82.

Khan AN, Irion KL, Kasthuri RS, et al. Extrinsic Allergic Alveolitis. emedicine. Last Updated: February 22, 2005. 19pp.

Sharma S. Hypersensitivity Pneumonitis. emedicine. Last Updated: March 8, 2005. 14pp.

The information in NORD’s Rare Disease Database is for educational purposes only. It should never be used for diagnostic or treatment purposes. If you have questions regarding a medical condition, always seek the advice of your physician or other qualified health professional. NORD’s reports provide a brief overview of rare diseases. For more specific information, we encourage you to contact your personal physician or the agencies listed as “Resources” on this report.

Report last updated: 2008/04/25 00:00:00 GMT+0

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