Farmer's lung

Farmer's lung
Classification and external resources
Specialty pulmonology
ICD-10 J67.0
ICD-9-CM 495.0
DiseasesDB 29636
eMedicine med/771
MeSH D005203

Farmer's lung (not to be confused with silo-filler's disease) is a hypersensitivity pneumonitis induced by the inhalation of biologic dusts coming from hay dust or mold spores or any other agricultural products.[1] It results in a type III hypersensitivity inflammatory response and can progress to become a chronic condition which is considered potentially dangerous.[2]

Hay shed - - 669503.jpg


The only cause of farmer’s lung is repeated exposure to tiny microorganisms which inhabit moldy hay. They are inhaled and often provoke the creation of IgE antibodies that circulate in the bloodstream, these types of immune response are most often initiated by exposure to thermophilic actinomycetes (most commonly Saccharopolyspora rectivirgula), which generates IgG-type antibodies. Following a subsequent exposure, IgG antibodies combine with the inhaled allergen to form immune complexes in the walls of the alveoli in the lungs.[3] This causes fluid, protein, and cells to accumulate in the alveolar wall which slows blood-gas interchange and compromises the function of the lung. After multiple exposures, it takes less and less of the antigens to set off the reaction in the lung.[4] The most prominent antigens are thermophilic actinomycetes and fungi.

Symptoms and Signs[]

Farmer’s lung reactions can be categorized as acute and chronic reactions. Acute and chronic reactions have the same symptoms but for chronic reactions, the symptoms are much more severe. Farmer’s lung symptoms include:

These symptoms develop between four and eight hours after exposure to the antigens. In acute attacks, the symptoms mimic pneumonia or flu. In chronic attacks, there is a possibility of the victim going into shock and dying from the attack.[5]

Length of Symptoms and Treatment[]

Depending on the severity of the symptoms, FLD can last from one to two weeks, or they can last for the rest of one’s life. Acute FLD has the ability to be treated because hypersensitivity to the antigens has not yet developed. The main treatment is rest and reducing the exposure to the antigens through masks and increased airflow in confined spaces where the antigens are present. Another treatment for acute FLD is pure oxygen therapy. For chronic FLD, there is no true treatment because the patient has developed hypersensitivity meaning their FLD could last the rest of their life. Any exposure to the antigens once hypersensitivity can set off another chronic reaction.[5]


The only prevention for FLD is ventilating the work areas putting workers at risk and using face masks to filter out the antigens attempting to enter the lungs through the air.


FLD affects approximately .5%-3% of farmers. In some regions of the world such as Asia, the rate is more around 6%.


  1. ^ Enelow, RI (2008). Fishman's Pulmonary Diseases and Disorders (4th ed.). McGraw-Hill. pp. 1161–1172. ISBN 0-07-145739-9. 
  2. ^
  3. ^ S., Geha, Raif (2008). Case studies in immunology : a clinical companion. Rosen, Fred S. (5th ed.). New York, N.Y.: Garland Science, Taylor and Francis Group. ISBN 9780815341451. OCLC 80460619. 
  4. ^ P., Kahn, Ada (2004). The encyclopedia of work-related illnesses, injuries, and health issues. New York, N.Y.: Facts on File. ISBN 9780816048441. OCLC 61131489. 
  5. ^ a b "National Ag Safety Database - National Ag Safety Database". Retrieved 2017-12-17.