Hypersensitivity pneumonitis risk factors

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]


The following is a partial list of occupations and major causative antigens that put a patient at risk of hypersensitivity pneumonitis. Microbial agents like fungi or bacteria in humidifiers, heating systems, and air conditioners found in homes and offices. Exposure to certain chemicals, such as isocyanates or acid anhydrides, can also increase the risk of hypersensitivity pneumonitis in susceptible individuals.

Risk factors

  • The most potent risk factor in the development of hypersensitivity pneumonitis is exposure to organic antigens.
  • Certain occupations that are more at risk to these exposures are:
    • Farmers and cattle workers
    • Poultry and other bird handlers[1]
      • These workers are exposed to droppings, feathers, and serum proteins of pigeons and other birds.
    • Ventilation workers[2]
      • These workers may be exposed to water-related contamination.
      • Microorganisms can colonize humidifiers, forced-air systems, hot tubs, whirlpools, and spas.
    • Veterinarians and animal handlers
      • Daily contact with a large variety of animals can lead to exposure to organic antigens.
    • Grain and flour processors and loaders
      • These workers are exposed to grain.
      • Grain may be colonized with a variety of microorganisms and their antigens.
    • Lumber mill workers and paper/wallboard manufacturers.[3]
      • These workers are exposed to wood which can become colonized with molds and then becomes aerosolized.
    • Plastic manufacturers, painters, and electronics industry workers
      • These workers can be exposed to diphenylmethane diisocyanate or toluene diisocyanate.
    • Textile workers
    • Mushroom cultivators
    • Wine makers


  1. Ahrer E, Philadelphy G, Bauer M (1969). "[Subcutaneous wire fixation of tibial torsion fractures]". Hefte Unfallheilkd (in German). 101: 63–91. PMID 5397797.
  2. Kane GC, Marx JJ, Prince DS (August 1993). "Hypersensitivity pneumonitis secondary to Klebsiella oxytoca. A new cause of humidifier lung". Chest. 104 (2): 627–9. PMID 8339664.
  3. Gamboa PM, de las Marinas MD, Antépara I, Jáuregui I, Sanz MM (1990). "Extrinsic allergic alveolitis caused by esparto (Stipa tenacissima)". Allergol Immunopathol (Madr). 18 (6): 331–4. PMID 2088103.

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