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Hypersensitivity pneumonitis


Related Terms
  • A. clavatus,air conditioner lung, Aspergillus clavatus,alveolitis, bagassosis, bird breeder's lung, bird fancier's lung, cheese worker's lung, chemical worker's lung, Cladosporium,coffee-worker's lung, detergent-worker's lung, epoxy-resin lung, extrinsic allergic alveolitis, farmer's lung, farm-worker's lung, grain handler's lung, HP, humidifier lung, hypersensitivity pneumonitides, laboratory-worker's lung, lifeguard lung, lung disease, lung inflammation, M. faeni, M. stolonifer,malt worker's lung, Micropolyspora faeni,miller's lung, mollusk shell hypersensitivity, Mucor stolonifer, mushroom picker's disease, occupational disease, P. casei,paprika splitter's lung, Penicillium casei,pneumonia, pneumonitides, pneumonitis, poultry-worker's lung, pulmonary disease, pulmonary fibrosis, S. granarius, S. rectivirgula, Saccharopolyspora rectivirgula, Sitophilus granarius, T. sacchari, T. vulgaris, Thermoactinomyces sacchari, Thermoactinomyces vulgaris,winemaker's lung, woodworker's lung.

  • Pneumonitis is a general term for inflammation of lung tissue.
  • Hypersensitivity pneumonitis (also called allergic alveolitis) is an inflammation in the lungs caused by exposure to an allergen, usually organic dust (like fungus spores from moldy hay or bird droppings). Since these allergens are common in certain lines of work (farming, for example), hypersensitivity pneumonitis is usually considered an occupational disease.
  • When a person inhales such allergens the first time, no symptoms appear. After repeated exposure to the allergen, the immune system of an allergic person becomes sensitized. Once sensitized, the immune system can quickly detect the allergen when it enters the body and produce antibodies called immunoglobulin E (IgE) to fight off the allergen. These antibodies trigger the release of chemical mediators, which cause allergy symptoms, such as hives, rash, teary eyes and runny nose.
  • Acute hypersensitivity pneumonitis may occur in sensitized individuals four to six hours after exposure to the allergen. The alveoli (tiny air sacs in the lung) become inflamed, and their walls fill up with white blood cells. In some cases, the sacs will fill with fluid. Chronic illness may develop after frequent exposure of high concentrations of the allergen. If the disease is chronic and recurs as a result of continued allergen exposure, parts of the lung may develop fibrous scar tissue (also known as pulmonary fibrosis) and may no longer function normally. At this point, the damage is usually irreversible.
  • The prevalence of hypersensitivity pneumonitis depends on the region, climate and farming practices. In the United States, it was estimated in 2003 that the disease affects 0.4-7% of the farming population. In the United Kingdom, it was estimated in 2003 there are between 420-3,000 cases of farmer's lung per 100,000 people at risk each year. In France, there are about 4,370 cases per 100,000 at risk each year. In Finland, there are a reported 1,400-1,700 cases per 100,000 people at risk each year.

Author information
  • This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (

  1. American Lung Association. Hypersensitivity Pneumonitis. .
  2. Lung Cancer Frontiers. Hypersensitivity Pneumonitis. .
  3. MedlinePlus. Hypersensitivity pneumonitis. .
  4. Natural Standard: The Authority on Integrative Medicine. .
  5. University of Pennsylvania Health System. Hypersensitivity Pneumonitis. .

  • Hypersensitivity pneumonitis occurs after exposure to inhaled allergens, such as dust, animal dander, mold spores or plants.
  • Hypersensitivity pneumonitis is typically considered an occupational illness and has unique names that reflect the associated occupation. More than 300 etiologies of hypersensitivity pneumonitis have been reported from a wide range of airborne antigens. Examples include: farmer's lung (due to thermophilic actinomycetes and other pathogens), winemaker's lung (due to Botrytis cinerea), coffee-worker's lung (due to coffee-bean dust), lifeguard lung (due to aerosolized endotoxin), bird-fancier's lung (due to avian antigens), laboratory-worker's lung (due to rodent antigens), miller's lung (due to wheat weevil), woodworker's lung (due to Penicillium chrysogenum), detergent-worker's lung (due to Bacillus subtilis) and epoxy-resin lung (due to phthalic anhydride).
  • Farmer's lung is the most common form of hypersensitivity pneumonitis. It is caused by thermophilic actinomycetes and other pathogens that grow on hay, straw, grains and other organic materials found on farms.
  • The most common type of hypersensitivity pneumonitis among children is called bird-fancier's lung. This disease is usually caused by allergens (avian or animal proteins) associated with small, caged birds that are kept as domesticated pets.
  • The summer form of the disease is typically found in Japan, where the condition is attributed to the growth of mold in older wooden homes during the hot, humid summer months when spores are released. This form clears up by mid autumn and recurs the following year in sensitive individuals who are continually exposed to the mold spore allergens.
  • There is no evidence that cigarette smoking causes hypersensitivity pneumonitis. However, smoking cigarettes may aggravate the symptoms of a person who has the disease. Tobacco smoke temporarily paralyzes the cilia (small hairs) the line the bronchial tubes. The cilia are designed to filter irritants out of the airways. However, when the cilia are paralyzed, irritants remain in the bronchial tubes and infiltrate the alveoli, inflaming the tissue and breaking down the elastic fibers.

  • Symptoms vary from mild to severe. Acute symptoms may last up to three weeks, and symptoms often include shortness of breath, cough, burning sensation in the chest, malaise, chills and fever. The symptoms may persist for as little as 12 hours or as long as 10 days. Between attacks, the person may experience no symptoms.
  • Chronic hypersensitivity pneumonitis lasts longer than three weeks. After repeated exposure to an allergen, a chronic cough may develop with excessive sputum, which often contains pus. The patient may also develop a chronic shortness of breath, decreased appetite and weight loss. Clubbing (enlarged fingers and toes) is seen in about 50% of patients with chronic hypersensitivity pneumonitis. Tachypnea (rapid breathing), respiratory distress and rales (crackling sound in the chest, as a result from fluid in the alveoli) may occur.
  • Chronic hypersensitivity pneumonitis may lead to pulmonary fibrosis (scarring of the lung tissue), which is usually irreversible.

  • Blood test: A qualified healthcare provider may perform a blood test to help detect allergies.
  • Challenge test: A challenge test may be performed under expert medical supervision to confirm a diagnosis. During the test, the individual inhales the suspected allergen in a controlled setting and the physician looks for symptoms. This type of test should only be performed by a qualified healthcare provider because it may provoke severe allergic reactions.
  • CT-scan: A high-resolution CT-scan of the lungs may be performed to confirm a diagnosis.
  • History: A detailed history is needed in order to determine whether the occurrence of symptoms may be related to environmental exposure.
  • Lung biopsy: A lung biopsy may be performed to distinguish the condition from other lung diseases. If an individual tests positive for the disease, findings may include small, poorly formed noncaseating granulomas near the respiratory or terminal bronchioles, patchy mononuclear cell infiltration (lymphocytes and plasma cells) of alveolar walls and large histiocytes with foamy cytoplasm in the interstitium.
  • Physical exam: During the physical exam, rales (crackling sound in the chest caused by fluid in the alveoli) may be heard when a healthcare provider listens to the patient's chest with a stethoscope.
  • X-ray: A chest X-ray and lung function test may show effects of the disease during acute episodes or during the chronic stage of the disease. However, the test results may appear normal between episodes when the patient shows no symptoms. These test results are not specific for hypersensitivity pneumonitis, and positive results may be due to other causes.

  • Antigen avoidance: Individuals should avoid exposure to known allergens because the condition is reversible, if diagnosed early. Most patients recover completely after avoiding exposure to allergens.
  • Corticosteroids: Corticosteroids (like prednisone) may help decrease inflammation in the lungs in the short-term. Corticosteroid therapy has helped relieve symptoms dramatically after one or two months, according to research. However, the same studies also found that corticosteroids did not offer any added benefit in the long-term when compared to antigen avoidance or placebo. While corticosteroids may help relieve symptoms, they cannot cure the disease.
  • It may take up to three weeks to fully recover from an acute attack. Lung damage, such as pulmonary fibrosis, is permanent and may occur even after symptoms have subsided.
  • Most patients who have farmer's lung recover with only minor functional abnormalities in the lungs. Many farmers develop mild chronic lung impairment.
  • Bird fancier's lung, although not as well studied, appears to have a worse prognosis than farmer's lung. According to some research, 30% of bird fancier's lung cases are fatal within five years. The poorer prognosis may be the result of exposure to higher concentrations of the antigen, as well as more frequent exposure in the home environment, according to researchers.

Integrative therapies
  • Note: Currently, there is insufficient evidence available on the safety and effectiveness of integrative therapies for the treatment of hypersensitivity pneumonitis. The integrative therapies listed below should be used only under the supervision of a qualified healthcare provider, and should not be used in replacement of other proven therapies or preventive measures.
  • Good scientific evidence:
  • Bromelain: Some physicians use bromelain, an enzyme derived from pineapple, to help reduce inflammation. It is sometimes recommended to be taken with turmeric (Curcuma longa), which may enhance the effects of bromelain.
  • Avoid if allergic to bromelain, pineapple, honeybee, venom, latex, birch pollen, carrots, celery, fennel, cypress pollen, grass pollen, papain, rye flour, wheat flour, or members of the Bromeliaceaefamily. Use cautiously with a history of bleeding disorders, stomach ulcers, or heart, liver, or kidney disease. Use caution before dental or surgical procedures or while driving or operating machinery. Avoid if pregnant or breastfeeding.
  • Yoga: Limited human study exists for yoga in the treatment of lung diseases, such as bronchitis, fluid around the lungs (pleural effusion), or airway obstruction. Better-designed research is necessary before any conclusions can be made.
  • Yoga is generally considered to be safe in healthy individuals when practiced appropriately. Avoid some inverted poses with disc disease of the spine, fragile or atherosclerotic neck arteries, risk for blood clots, extremely high or low blood pressure, glaucoma, detachment of the retina, ear problems, severe osteoporosis, or cervical spondylitis. Certain yoga breathing techniques should be avoided in people with heart or lung disease. Use cautiously with a history of psychotic disorders. Yoga techniques are believed to be safe during pregnancy and breastfeeding when practiced under the guidance of expert instruction (the popular Lamaze techniques are based on yogic breathing). However, poses that put pressure on the uterus, such as abdominal twists, should be avoided in pregnancy.
  • Unclear or conflicting scientific evidence:
  • Black seed: Studies in patients with allergies found that black seed decreased allergic disease severity, slightly decreased plasma triglycerides (levels of fat within the blood), and slightly increased HDL cholesterol. The effect of black seed for allergies is still not clear and further study is required.
  • Avoid with a known allergy/hypersensitivity to black seed, its constituents, black seed oil, or to members of the Ranunculaceae family. Allergic contact dermatitis has been reported after topical use of black seed or the oil from the seed.
  • Cat's claw: Cat's claw may have anti-inflammatory effects, which has led to research of this herb for conditions such as allergies. Large, high-quality human studies are needed comparing effects of cat's claw alone vs. placebo.
  • Avoid if allergic to cat's claw or Uncaria plants or plants in the Rubiaceae family such as gardenia, coffee, or quinine. Avoid with a history of conditions affecting the immune system (such as AIDS, HIV, some types of cancer, multiple sclerosis, tuberculosis, rheumatoid arthritis, lupus). Use cautiously with bleeding disorders or a history of stroke, or if taking drugs that may increase the risk of bleeding. Discontinue use two weeks before surgery/dental/diagnostic procedures with bleeding risk, and do not use immediately after these procedures. Cat's claw may be contaminated with other Uncaria species. Reports exist of a potentially toxic, Texan grown plant, Acacia gregii being substituted for cat's claw. Avoid if pregnant, breastfeeding, or trying to become pregnant.
  • Dandelion: Research in laboratory animals suggests that dandelion root may possess anti-inflammatory properties. There is a lack of well-conducted human studies currently available in this area.
  • Avoid if allergic to chamomile, feverfew, honey, yarrow, or any related plants such as aster, daisies, sunflower, chrysanthemum, mugwort, ragweed, or ragwort. Use cautiously with diabetes or bleeding disorders, gastroesophageal reflux disease (GERD), kidney or liver diseases, or a history of stroke or electrolyte disorders. Potassium blood levels should be monitored. Stop use two weeks before surgery/dental/diagnostic procedures with bleeding risk and do not use immediately after these procedures. Avoid if pregnant or breastfeeding.
  • Euphorbia: Euphorbia balsamifera has been studied in patients with acute dental pulpitis, and may be comparable to that of pulpal nerve caustics. Additional study is necessary to make a recommendation for inflammation.
  • Avoid if allergic or hypersensitive to pollen from Euphorbia fulgens. Use cautiously with history of Epstein Barr virus infection or stomach conditions. Avoid if pregnant or breastfeeding.
  • Eyebright: Several iridoid glycosides isolated from eyebright, particularly aucubin, may possess anti-inflammatory properties comparable to those of indomethacin (a nonsteroidal anti-inflammatory drug). However, there is currently insufficient evidence to recommend for or against eyebright as an anti-inflammatory agent.
  • Avoid with a known allergy or hypersensitivity to eyebright. Hypersensitivity to members of the Scrophulariaceae family may lead to a cross-sensitivity reaction. Use cautiously as an eye treatment, particularly homemade preparations, due to the risk of infection if not sterile. Use cautiously with diabetes and drugs that are broken down by the liver. Avoid if pregnant or breastfeeding.
  • Ginseng: Several studies have looked at the effects of ginseng in a variety of lung conditions. More research is needed.
  • Avoid ginseng if known allergy to plants in the Araliaceae family. There has been a report of a serious life-threatening skin reaction, possibly caused by contaminants in ginseng formulations.
  • Hypnotherapy: It has been suggested that hypnotherapy may be effective for allergies. However, further research is necessary to determine whether it is an effective treatment for this indication.
  • Use cautiously with mental illnesses (e.g. psychosis, schizophrenia, manic depression, multiple personality disorder, or dissociative disorders) or seizure disorders.
  • Kiwi: Kiwi (Actinidia deliciosa, Actinidia chinensis) may be beneficial in lung conditions such as upper respiratory infections (including colds). However, scientific data is lacking. Limited available study suggests that kiwi, and other fruits high in vitamin C, may have a protective effect on lung conditions in children, especially wheezing. However, properly controlled studies are lacking at this time on the use of kiwi for prevention of respiratory problems.
  • Avoid if allergic or hypersensitive to kiwi, latex, birch pollen, banana, chestnut, fig, flour, melon, poppy seeds, rye grain, sesame seeds and related substances. Kiwi is generally considered safe when taken in amounts naturally found in foods. Use cautiously with anti-platelet drugs like aspirin, cilostazol or clopidogrel. Use cautiously with hormone therapies or serotonergic drugs. Avoid if pregnant or breastfeeding. The amount found in foods appears to be safe in most people.
  • Lactobacillus acidophilus: Limited available study suggests that the Lactobacillus acidophilus (L. acidophilus) strain L-92 (L-92) may be effective for the treatment of Japanese cedar-pollen allergy. Further research is needed to confirm these results.
  • L. acidophilus may be difficult to tolerate if allergic to dairy products containing L. acidophilus. Avoid with history of an injury or illness of the intestinal wall, immune-disease, or heart valve surgery. Avoid with prescription drugs, such as corticosteroids, because of the risk of infection. Use cautiously with heart murmurs. Antibiotics or alcohol may destroy L. acidophilus. Therefore, it is recommended that L. acidophilus be taken three hours after taking antibiotics or drinking alcohol. Some individuals may use antacids, such as famotidine (Pepcid®) and esomeprazole (Nexium®), to decrease the amount of acid in the stomach one hour before taking L. acidophilus.
  • L-carnitine: Currently there is insufficient evidence to support the use of carnitine for respiratory distress.
  • Avoid with known allergy or hypersensitivity to carnitine. Use cautiously with peripheral vascular disease, hypertension (high blood pressure), alcohol-induced liver cirrhosis, or diabetes. Use cautiously in low birth weight infants and individuals on hemodialysis. Use cautiously if taking anticoagulants (blood thinners), beta-blockers, or calcium channel blockers. Avoid if pregnant or breastfeeding.
  • Licorice: Many medical conditions are marked by inflammation. Because licorice can affect the metabolism of steroids, licorice is sometimes used to help decrease inflammation. Additional study is needed to make a conclusion.
  • Avoid with a known allergy to licorice, any component of licorice, or any member of the Fabaceae (Leguminosae) plant family. Avoid with congestive heart failure, coronary heart disease, kidney or liver disease, fluid retention, high blood pressure, hormonal abnormalities or if taking diuretics. Licorice can cause abnormally low testosterone levels in men or high prolactin or estrogen levels in women. This may make it difficult to become pregnant and may cause menstrual abnormalities.
  • Lutein: Lutein is found in high levels in foods such as green vegetables, egg yolk, kiwi fruit, grapes, orange juice, zucchini, squash, and corn. For some commercially available supplements, lutein is extracted from marigold petals.There is early evidence of a role of carotenoids in lung function and severity of respiratory infections. More research is needed to make a conclusion.
  • Avoid if allergic or hypersensitive to lutein or zeaxanthin. Use cautiously if at risk for cardiovascular disease or cancer. Avoid if pregnant or breastfeeding.
  • Onion: Early research shows that topical application of an alcoholic onion extract significantly reduced responses to allergies, such as wheals (hives) and flares. More research is needed.
  • Avoid if allergic or hypersensitive to onion (Allium cepa), its constituents, or members of the Lilaceae family. Use cautiously with hematologic (blood) disorders, diabetes, hypoglycemia (low blood sugar), and hypotension (low blood pressure). Use cautiously if taking anticoagulants or antiplatelets (blood thinners). Avoid medicinal doses if pregnant or breastfeeding.
  • Perilla: Preliminary evidence suggests some benefit of perilla extract for seasonal allergies. Further clinical trials are required before conclusions can be made.
  • Avoid if allergic/hypersensitive to perilla or members of the Lamiaciae/Labiatae family. Use cautiously with cancer, low HDL-cholesterol, and immune disorders. Use cautiously if taking NSAIDS or barbiturates. Avoid if pregnant or breastfeeding.
  • Physical therapy: Lung hyperinflation is a technique used by physiotherapists to mobilize and remove excess lung secretions, reinflate areas of pulmonary collapse, and improve oxygenation. Additional research is needed to better understand the effectiveness of physical therapy for pulmonary conditions.
  • Not all physical therapy programs are suited for everyone, and patients should discuss their medical history with their qualified healthcare professionals before beginning any treatments. Based on the available literature, physical therapy appears generally safe when practiced by a qualified physical therapist; however, complications are possible. Persistent pain and fractures of unknown origin have been reported. Physical therapy may increase the duration of pain or cause limitation of motion. Pain and anxiety may occur during the rehabilitation of patients with burns. Both morning stiffness and bone erosion have been reported in the physical therapy literature, although causality is unclear. Erectile dysfunction has also been reported. All therapies during pregnancy and breastfeeding should be discussed with a licensed obstetrician/gynecologist before initiation.
  • Probiotics: Only a few types and combinations of probiotics have been studied as a possible allergy treatment. They have been studied mostly in children, teenagers, and young adults. Further research is necessary before a firm conclusion can be made.
  • Probiotics are generally considered safe and well tolerated. Avoid if allergic or hypersensitive to probiotics. Use cautiously if lactose intolerant.
  • Thymus extract: Thymus extract may reduce allergy symptoms due to its potential immune stimulating effects. More clinical trials are required before recommendations can be made involving thymus extract for this use.
  • Avoid if allergic or hypersensitive to thymus extracts. Use bovine thymus extract supplements cautiously due to potential for exposure to the virus that causes "mad cow disease." Avoid use with an organ transplant or other forms of allografts or xenografts. Avoid if receiving immunosuppressive therapy, with thymic tumors, myasthenia gravis (neuromuscular disorder), untreated hypothyroidism, or if taking hormonal therapy. Avoid if pregnant or breastfeeding; thymic extract increases human sperm motility and progression.
  • Turmeric: Turmeric is a perennial plant native to India and Indonesia, and it is often used as a spice in cooking. Laboratory and animal studies show activity against inflammation for turmeric and its constituent curcumin. Reliable human research is lacking.
  • Avoid if allergic or hypersensitive to turmeric (curcumin), yellow food colorings or plants belonging to the Curcuma or Zingiberaceae (ginger) families. Use cautiously with history of bleeding disorders, immune system deficiencies, liver disease or gallstones. Use cautiously with blood-thinners (e.g. warfarin). Use cautiously if pregnant or breastfeeding.
  • Yerba santa: Chumash Native Americans and other California tribes have used yerba santa (Eriodictyon californicum) and other related species (Eriodictyon crassifolium, Eriodictyon trichocalyx) for many centuries in the treatment of pulmonary conditions, saliva production, and to stop bleeding of minor cuts and scrapes. There is also clinical history of the use of Eriodictyon extracts in influenza, bacterial pneumonia, asthma, bronchitis, and tuberculosis. However, additional study is needed.
  • Avoid if allergic or hypersensitive to Eriodictyon species. Use cautiously in children. Avoid if pregnant or breastfeeding.

  • Avoid exposure to known allergens.
  • Properly dry and store farm products to decrease the risk of developing hypersensitivity pneumonitis.
  • Individuals who may be exposed to allergens should work in ventilated areas and use respiratory protection (masks).

Increased risk
  • Most individuals who have hypersensitivity pneumonitis are exposed to allergens (usually organic dusts) in daily work or personal life. The risk is greater when individuals are exposed frequently to high concentrations of the substances.
  • However, it is estimated that only about 5-20% of individuals exposed to the known allergens develop the disease.

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The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.

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