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Hypersensitivity pneumonitis

Last edited: 4/14/2026

Overview

Hypersensitivity pneumonitis (HP) is an interstitial lung disease caused by inhalation of organic antigens leading to an immune-mediated inflammatory response in susceptible individuals 48.

Diagnosis

  • Clinical history: Exposure to environmental antigens is crucial 4.
  • Physical examination: Often reveals signs of interstitial lung disease 4.
  • Laboratory tests: Elevated inflammatory markers may be present 4.
  • Pulmonary function tests: Show restrictive pattern or impaired gas exchange 4.
  • High-resolution computed tomography (HRCT): Characteristic findings include ground-glass opacities, interlobular septal thickening, and centrilobular nodules 22.
  • Bronchoalveolar lavage (BAL): Lymphocytosis, particularly with increased CD4/CD8 ratio, supports the diagnosis 28.
  • Serum precipitins: Presence against environmental antigens can confirm exposure 428.
  • Provocation testing: Used cautiously to confirm diagnosis when clinical suspicion is high 4.

    • Management

  • Avoidance of antigens: Primary intervention to prevent disease progression 4.
  • Corticosteroids: First-line treatment for acute exacerbations or severe disease 4 (Evidence: Strong 4).
  • Immunosuppressive agents: Considered for refractory cases; examples include azathioprine, mycophenolate mofetil 4 (Evidence: Moderate 4).
  • Pirfenidone: Shown to have potential in slowing disease progression in fibrotic HP 3 (Evidence: Moderate 3).
  • Supportive care: Includes pulmonary rehabilitation and management of symptoms 4.

    • Special Populations

  • Pregnancy: Limited data; management focuses on symptom control and avoidance of triggers 4.
  • Pediatrics: Diagnosis and management similar to adults but requires careful monitoring due to growth considerations 4.
  • Elderly: Increased risk of comorbidities; management tailored to overall health status 4.
  • Comorbidities: Presence of other respiratory conditions may complicate diagnosis and treatment; individualized care plans are essential 4.

    • Key Recommendations

  • Identify and avoid environmental antigens to prevent disease progression and exacerbations (Evidence: Strong 4).
  • Initiate corticosteroid therapy for acute exacerbations or severe disease (Evidence: Strong 4).
  • Consider immunosuppressive agents for patients with refractory disease (Evidence: Moderate 4).
  • Use HRCT and BAL to support diagnosis when clinical suspicion is high (Evidence: Moderate 2228).
  • Monitor and manage comorbidities carefully in elderly patients to tailor treatment effectively (Evidence: Expert opinion 4).

    • References

    1 Ridge A, Cooling N, Seidel B. A mixed immediate and delayed allergy to oral vitamin D supplementation: a case report. Journal of medical case reports 2025. link 2 Lis K. Biotin Supplementation-The Cause of Hypersensitivity and Significant Interference in Allergy Diagnostics. Nutrients 2025. link 3 Fernández Pérez ER, Crooks JL, Lynch DA, Humphries SM, Koelsch TL, Swigris JJ et al.. Pirfenidone in fibrotic hypersensitivity pneumonitis: a double-blind, randomised clinical trial of efficacy and safety. Thorax 2023. link 4 Fernández Pérez ER, Travis WD, Lynch DA, Brown KK, Johannson KA, Selman M et al.. Diagnosis and Evaluation of Hypersensitivity Pneumonitis: CHEST Guideline and Expert Panel Report. Chest 2021. link 5 Arasi S, Mastrorilli C, Pecoraro L, Giovannini M, Mori F, Barni S et al.. Heiner Syndrome and Milk Hypersensitivity: An Updated Overview on the Current Evidence. Nutrients 2021. link 6 Melchiors BLB, Garvey LH. Investigation of perioperative hypersensitivity reactions: an update. Current opinion in allergy and clinical immunology 2020. link 7 Izquierdo-Domínguez A, Bobolea I, Doña I, Campo P, Segura C, Ortega N et al.. Statement of the Spanish Society of Allergology and Clinical Immunology on Provocation Tests With Aspirin/Nonsteroidal Anti-inflammatory Drugs. Journal of investigational allergology & clinical immunology 2020. link 8 Miller R, Allen TC, Barrios RJ, Beasley MB, Burke L, Cagle PT et al.. Hypersensitivity Pneumonitis A Perspective From Members of the Pulmonary Pathology Society. Archives of pathology & laboratory medicine 2018. link 9 Laguna JJ, Archilla J, Doña I, Corominas M, Gastaminza G, Mayorga C et al.. Practical Guidelines for Perioperative Hypersensitivity Reactions. Journal of investigational allergology & clinical immunology 2018. link 10 Mourad AA, Bahna SL. Hypersensitivities to non-steroidal anti-inflammatory drugs. Expert review of clinical immunology 2014. link 11 Schalock PC, Thyssen JP. Patch testers' opinions regarding diagnostic criteria for metal hypersensitivity reactions to metallic implants. Dermatitis : contact, atopic, occupational, drug 2013. link 12 McCabe D, Altman KW. Laryngeal hypersensitivity in the World Trade Center-exposed population: the role for respiratory retraining. American journal of respiratory and critical care medicine 2012. link 13 Leventhal JS, Berger EM, Brauer JA, Cohen DE. Hypersensitivity reactions to vaccine constituents: a case series and review of the literature. Dermatitis : contact, atopic, occupational, drug 2012. link 14 Kim MH, Park CH, Kim DI, Kim KM, Kim HK, Lim KH et al.. Surveillance of contrast-media-induced hypersensitivity reactions using signals from an electronic medical recording system. Annals of allergy, asthma & immunology : official publication of the American College of Allergy, Asthma, & Immunology 2012. link 15 . Propolis: hypersensitivity reactions. Prescrire international 2010. link 16 Fritsche PJ, Helbling A, Ballmer-Weber BK. Vaccine hypersensitivity--update and overview. Swiss medical weekly 2010. link 17 Tillberg A, Stenberg B, Berglund A. Reactions to resin-based dental materials in patients--type, time to onset, duration, and consequence of the reaction. Contact dermatitis 2009. link 18 Coggon D. Health risks from mobile phone base stations. Occupational and environmental medicine 2006. link 19 Johnson T, Dietrich J, Hagan L. Management of stinging insect hypersensitivity: a 5-year retrospective medical record review. Annals of allergy, asthma & immunology : official publication of the American College of Allergy, Asthma, & Immunology 2006. link60017-8) 20 Markel A. Allopurinol-induced DRESS syndrome. The Israel Medical Association journal : IMAJ 2005. link 21 Gomes ER, Demoly P. Epidemiology of hypersensitivity drug reactions. Current opinion in allergy and clinical immunology 2005. link 22 Herráez I, Gutierrez M, Alonso N, Allende J. Hypersensitivity pneumonitis producing a BOOP-like reaction: HRCT/pathologic correlation. Journal of thoracic imaging 2002. link 23 Tamburro JE, Esterly NB. Hypersensitivity syndromes. Adolescent medicine (Philadelphia, Pa.) 2001. link 24 Pluim HJ, van Deuren M, Wetzels JF. The allopurinol hypersensitivity syndrome. The Netherlands journal of medicine 1998. link00088-0) 25 Nakazawa T, Umegae Y. Sericulturist's lung disease: hypersensitivity pneumonitis related to silk production. Thorax 1990. link 26 Calabrese LH, Michel BA, Bloch DA, Arend WP, Edworthy SM, Fauci AS et al.. The American College of Rheumatology 1990 criteria for the classification of hypersensitivity vasculitis. Arthritis and rheumatism 1990. link 27 Singer JZ, Wallace SL. The allopurinol hypersensitivity syndrome. Unnecessary morbidity and mortality. Arthritis and rheumatism 1986. link 28 Cormier Y, Bélanger J, Beaudoin J, Laviolette M, Beaudoin R, Hebert J. Abnormal bronchoalveolar lavage in asymptomatic dairy farmers. Study of lymphocytes. The American review of respiratory disease 1984. link 29 Weiss MM, Petersen RC. Electromagnetic radiation emitted from video computer terminals. American Industrial Hygiene Association journal 1979. link 30 Parker D, Turk JL. Delay in the development of the allergic response to metals following intratracheal instillation. International archives of allergy and applied immunology 1978. link 31 Schwartz HJ, Chester EH, Fink JN, Payne CB, Baum GL. On respirable organic antigens, mattresses and some idiopathic lung diseases. Annals of allergy 1978. link 32 Olenchock SA. Animal models of hypersensitivity pneumonitis: a review. Annals of allergy 1977. link 33 Marinkovich VA, Hill A. Hypersensitivity alveolitis. JAMA 1975. link 34 Wilkie BN, Gygax M, Pauli B. Immunofluorescent studies of bovine hypersensitivity pneumonitis. Canadian journal of comparative medicine : Revue canadienne de medecine comparee 1974. link 35 van Toorn DW. Coffee worker's lung. A new example of extrinsic allergic alveolitis. Thorax 1970. link 36 David JR, Schlossman SF. Immunochemical studies on the specificity of cellular hypersensitivity. The in vitro inhibition of peritoneal exudate cell migration by cehmically defined antigens. The Journal of experimental medicine 1968. link 37 Leskowitz S, Jones VE, Zak SJ. Immunochemical study of antigenic specificity in delayed hypersensitivity. V. Immunization with monovalent low molecular weight conjugates. The Journal of experimental medicine 1966. link

    Original source

    1. [1]
      A mixed immediate and delayed allergy to oral vitamin D supplementation: a case report. — Ridge A, Cooling N, Seidel B Journal of medical case reports (2025)
    2. [2]
      Biotin Supplementation-The Cause of Hypersensitivity and Significant Interference in Allergy Diagnostics. — Lis K Nutrients (2025)
    3. [3]
      Pirfenidone in fibrotic hypersensitivity pneumonitis: a double-blind, randomised clinical trial of efficacy and safety. — Fernández Pérez ER, Crooks JL, Lynch DA, Humphries SM, Koelsch TL, Swigris JJ et al. Thorax (2023)
    4. [4]
      Diagnosis and Evaluation of Hypersensitivity Pneumonitis: CHEST Guideline and Expert Panel Report. — Fernández Pérez ER, Travis WD, Lynch DA, Brown KK, Johannson KA, Selman M et al. Chest (2021)
    5. [5]
      Heiner Syndrome and Milk Hypersensitivity: An Updated Overview on the Current Evidence. — Arasi S, Mastrorilli C, Pecoraro L, Giovannini M, Mori F, Barni S et al. Nutrients (2021)
    6. [6]
      Investigation of perioperative hypersensitivity reactions: an update. — Melchiors BLB, Garvey LH Current opinion in allergy and clinical immunology (2020)
    7. [7]
      Statement of the Spanish Society of Allergology and Clinical Immunology on Provocation Tests With Aspirin/Nonsteroidal Anti-inflammatory Drugs. — Izquierdo-Domínguez A, Bobolea I, Doña I, Campo P, Segura C, Ortega N et al. Journal of investigational allergology & clinical immunology (2020)
    8. [8]
      Hypersensitivity Pneumonitis A Perspective From Members of the Pulmonary Pathology Society. — Miller R, Allen TC, Barrios RJ, Beasley MB, Burke L, Cagle PT et al. Archives of pathology & laboratory medicine (2018)
    9. [9]
      Practical Guidelines for Perioperative Hypersensitivity Reactions. — Laguna JJ, Archilla J, Doña I, Corominas M, Gastaminza G, Mayorga C et al. Journal of investigational allergology & clinical immunology (2018)
    10. [10]
      Hypersensitivities to non-steroidal anti-inflammatory drugs. — Mourad AA, Bahna SL Expert review of clinical immunology (2014)
    11. [11]
      Patch testers' opinions regarding diagnostic criteria for metal hypersensitivity reactions to metallic implants. — Schalock PC, Thyssen JP Dermatitis : contact, atopic, occupational, drug (2013)
    12. [12]
      Laryngeal hypersensitivity in the World Trade Center-exposed population: the role for respiratory retraining. — McCabe D, Altman KW American journal of respiratory and critical care medicine (2012)
    13. [13]
      Hypersensitivity reactions to vaccine constituents: a case series and review of the literature. — Leventhal JS, Berger EM, Brauer JA, Cohen DE Dermatitis : contact, atopic, occupational, drug (2012)
    14. [14]
      Surveillance of contrast-media-induced hypersensitivity reactions using signals from an electronic medical recording system. — Kim MH, Park CH, Kim DI, Kim KM, Kim HK, Lim KH et al. Annals of allergy, asthma & immunology : official publication of the American College of Allergy, Asthma, & Immunology (2012)
    15. [15]
      Propolis: hypersensitivity reactions. Prescrire international (2010)
    16. [16]
      Vaccine hypersensitivity--update and overview. — Fritsche PJ, Helbling A, Ballmer-Weber BK Swiss medical weekly (2010)
    17. [17]
      Reactions to resin-based dental materials in patients--type, time to onset, duration, and consequence of the reaction. — Tillberg A, Stenberg B, Berglund A Contact dermatitis (2009)
    18. [18]
      Health risks from mobile phone base stations. — Coggon D Occupational and environmental medicine (2006)
    19. [19]
      Management of stinging insect hypersensitivity: a 5-year retrospective medical record review. — Johnson T, Dietrich J, Hagan L Annals of allergy, asthma & immunology : official publication of the American College of Allergy, Asthma, & Immunology (2006)
    20. [20]
      Allopurinol-induced DRESS syndrome. — Markel A The Israel Medical Association journal : IMAJ (2005)
    21. [21]
      Epidemiology of hypersensitivity drug reactions. — Gomes ER, Demoly P Current opinion in allergy and clinical immunology (2005)
    22. [22]
      Hypersensitivity pneumonitis producing a BOOP-like reaction: HRCT/pathologic correlation. — Herráez I, Gutierrez M, Alonso N, Allende J Journal of thoracic imaging (2002)
    23. [23]
      Hypersensitivity syndromes. — Tamburro JE, Esterly NB Adolescent medicine (Philadelphia, Pa.) (2001)
    24. [24]
      The allopurinol hypersensitivity syndrome. — Pluim HJ, van Deuren M, Wetzels JF The Netherlands journal of medicine (1998)
    25. [25]
      Sericulturist's lung disease: hypersensitivity pneumonitis related to silk production. — Nakazawa T, Umegae Y Thorax (1990)
    26. [26]
      The American College of Rheumatology 1990 criteria for the classification of hypersensitivity vasculitis. — Calabrese LH, Michel BA, Bloch DA, Arend WP, Edworthy SM, Fauci AS et al. Arthritis and rheumatism (1990)
    27. [27]
      The allopurinol hypersensitivity syndrome. Unnecessary morbidity and mortality. — Singer JZ, Wallace SL Arthritis and rheumatism (1986)
    28. [28]
      Abnormal bronchoalveolar lavage in asymptomatic dairy farmers. Study of lymphocytes. — Cormier Y, Bélanger J, Beaudoin J, Laviolette M, Beaudoin R, Hebert J The American review of respiratory disease (1984)
    29. [29]
      Electromagnetic radiation emitted from video computer terminals. — Weiss MM, Petersen RC American Industrial Hygiene Association journal (1979)
    30. [30]
      Delay in the development of the allergic response to metals following intratracheal instillation. — Parker D, Turk JL International archives of allergy and applied immunology (1978)
    31. [31]
      On respirable organic antigens, mattresses and some idiopathic lung diseases. — Schwartz HJ, Chester EH, Fink JN, Payne CB, Baum GL Annals of allergy (1978)
    32. [32]
      Animal models of hypersensitivity pneumonitis: a review. — Olenchock SA Annals of allergy (1977)
    33. [33]
      Hypersensitivity alveolitis. — Marinkovich VA, Hill A JAMA (1975)
    34. [34]
      Immunofluorescent studies of bovine hypersensitivity pneumonitis. — Wilkie BN, Gygax M, Pauli B Canadian journal of comparative medicine : Revue canadienne de medecine comparee (1974)
    35. [35]
      Coffee worker's lung. A new example of extrinsic allergic alveolitis. — van Toorn DW Thorax (1970)
    36. [36]
      Immunochemical studies on the specificity of cellular hypersensitivity. The in vitro inhibition of peritoneal exudate cell migration by cehmically defined antigens. — David JR, Schlossman SF The Journal of experimental medicine (1968)
    37. [37]
      Immunochemical study of antigenic specificity in delayed hypersensitivity. V. Immunization with monovalent low molecular weight conjugates. — Leskowitz S, Jones VE, Zak SJ The Journal of experimental medicine (1966)
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