Rochester, Minnesota


Hagan.John@mayo.edu Clinical Profile


The research of John B. Hagan, M.D., focuses on several interrelated areas broadly relating to allergy, asthma and immunology. Dr. Hagan's major areas of interest include asthma and rhinosinusitis.

The mucous membranes of the nose, sinuses and bronchi serve as the major immune defense against inhaled pathogens, such as viruses and bacteria, and allergens, such as ragweed pollen and mold spores. Investigations to characterize inflammation of this mucosa, particularly eosinophilic inflammation, may allow for assessment and monitoring of asthma and chronic rhinosinusitis. The goals of Dr. Hagan's research team are to monitor eosinophils in respiratory secretions and blood as well as steroid or steroid metabolites, which together may help document adherence, identify steroid resistance, and allow for individualized treatment in specific patients who have conditions such as eosinophilic asthma and chronic rhinosinusitis with nasal polyps.

Focus areas

  • Chronic rhinosinusitis and eosinophilic inflammation. Recent efforts include obtaining nasal and sinus material for tissue culture and evaluating disease exacerbations to advance collaborative investigations of chronic rhinosinusitis, as well as defining mechanisms of eosinophilic inflammation in human diseases. In conjunction with Hirohito Kita, M.D., of the Division of Allergic Diseases, Dr. Hagan is working to improve the understanding of allergen-induced interleukin-33 release by the airway epithelium, characterizing alternaria and ribonucleases in T-helper type 2 immunity, and identifying type 2 innate lymphoid cells in asthma.
  • Treatment of moderate and severe asthma. Dr. Hagan has served as a primary investigator at Mayo Clinic's campus in Minnesota for recent clinical trials of biologic agents to treat patients with moderate and severe asthma. His collaborative group has published meta-analyses of asthma studies to improve understanding of asthma step-down care.
  • Food allergies and anaphylaxis. Another major focus, in conjunction with colleagues in the emergency department, has been to validate the National Institute of Allergy and Infectious Diseases and Food Allergy and Anaphylaxis Network criteria for the diagnosis of anaphylaxis in emergency department patients and to evaluate risk factors for exacerbation in these patients.
  • Immunodeficiency. An additional area of focus includes collaborative study of immunodeficiency patient groups, including common variable immunodeficiency, Bruton's (X-linked) agammaglobulinemia and Wiskott-Aldrich Syndrome, as well as studies regarding the administration of immunoglobulin therapies such as subcutaneous immunoglobulin.
  • Other collaborative efforts have involved the following: food allergy, radiologic and endoscopy changes associated with chronic rhinosinusitis, recombinant human C1 inhibitor, asthma phenotyping, and assessing educational programs in allergy and immunology.

Significance to patient care

Asthma is estimated to affect 25.5 million people in the U.S., causing over 1.5 million emergency room visits, 430,000 hospitalizations and 3,400 deaths each year. Chronic sinusitis, which commonly occurs with asthma, is estimated to affect 28.5 million adults in the U.S. each year. Dr. Hagan's goal is to improve patient outcomes through improved diagnoses and development of individualized treatments.


Primary Appointment

  1. Consultant, Division of Allergic Diseases, Department of Internal Medicine

Academic Rank

  1. Associate Professor of Medicine


  1. Fellow Allergy and Immunology, Programs in Rochester, Mayo School of Graduate Medical Education, Mayo Clinic College of Medicine
  2. Resident Allergy and Immunology, Programs in Rochester, Mayo School of Graduate Medical Education, Mayo Clinic College of Medicine
  3. Fellow - Critical Care Medicine Mayo Clinic in Rochester
  4. Resident Iowa Medicaid
  5. Resident Allergy and Immunology, Programs in Rochester, Mayo School of Graduate Medical Education, Mayo Clinic College of Medicine
  6. Resident - Internal Medicine Mayo Clinic in Rochester
  7. MD University of Tennessee, Memphis
  8. BA - Biology and Latin Baylor University

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