Overview
Hypersensitivity pneumonitis (HP), also called extrinsic allergic alveolitis (EAA), is a lung disease caused by the immune system overreacting to certain substances that are breathed in. When a person with HP is repeatedly exposed to triggers like mold, bird droppings, certain chemicals, or dust from hay or grain, their immune system attacks the lungs as if those substances were dangerous invaders. Over time, this causes inflammation deep inside the lungs. HP can be acute (coming on suddenly after a large exposure), subacute (building up over weeks), or chronic (developing slowly over months or years with ongoing low-level exposure). In the chronic form, the lungs can develop permanent scarring called fibrosis, which makes breathing harder and harder over time. Common symptoms include shortness of breath, a dry cough, fatigue, and sometimes fever and chills after exposure to the trigger. Treatment focuses on identifying and completely avoiding the trigger substance, which is the most important step. Doctors may also prescribe corticosteroids like prednisone to reduce inflammation. In advanced cases with significant scarring, additional medications used for pulmonary fibrosis may be considered. Early diagnosis and trigger avoidance give the best chance of stopping or slowing the disease.
Also known as:
Key symptoms:
Shortness of breath, especially with activityDry or productive coughFatigue and low energyFever and chills (especially in acute episodes)Chest tightnessLoss of appetite and unintended weight lossMuscle achesSymptoms that improve when away from home or work and worsen on returnCrackling sounds in the lungs heard by a doctorBluish tint to lips or fingertips in severe cases
Multifactorial
Caused by a mix of several genes and environmental factors
Variable
Can begin at different ages, from infancy through adulthood
FDA & Trial Timeline
10 eventsUniversity Hospitals Cleveland Medical Center — NA
Weill Medical College of Cornell University — NA
University of British Columbia — NA
Nantes University Hospital
Centre Hospitalier Universitaire de Besancon — NA
University of California, Los Angeles — EARLY_PHASE1
University of Kansas Medical Center
National Jewish Health
Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.
Treatments
No FDA-approved treatments are currently listed for Hypersensitivity pneumonitis.
9 clinical trialsare actively recruiting — trials can provide access to cutting-edge therapies.
View clinical trials →Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to Hypersensitivity pneumonitis.
Community
No community posts yet. Be the first to share your experience with Hypersensitivity pneumonitis.
Start the conversation →Latest news about Hypersensitivity pneumonitis
Disease timeline:
New recruiting trial: FAPI PET for Lung Fibrosis
A new clinical trial is recruiting patients for Hypersensitivity pneumonitis
New recruiting trial: Reimagining Interventions for Support and Education in Hypersensitivity Pneumonitis
A new clinical trial is recruiting patients for Hypersensitivity pneumonitis
New recruiting trial: P4O2 ILD Extension
A new clinical trial is recruiting patients for Hypersensitivity pneumonitis
New recruiting trial: Database and Biobank of Patients With Hypersensitivity Pneumonitis
A new clinical trial is recruiting patients for Hypersensitivity pneumonitis
New recruiting trial: Skeletal Muscle Function in Interstitial Lung Disease
A new clinical trial is recruiting patients for Hypersensitivity pneumonitis
New recruiting trial: Interstitial Lung Disease Research Unit Biobank
A new clinical trial is recruiting patients for Hypersensitivity pneumonitis
Caregiver Resources
NORD Caregiver Resources
Support, advocacy, and financial assistance for caregivers of rare disease patients.
Mental Health Support
Rare disease caregiving can be isolating. Connect with counseling and peer support.
Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Questions for your doctor
Bring these to your next appointment
- Q1.What is my specific trigger, and how can I confirm it and completely avoid it?,Do I have acute, subacute, or chronic HP, and what does that mean for my treatment and outlook?,Should I start corticosteroids, and what are the risks and benefits for my situation?,Is there any permanent scarring in my lungs already, and if so, what are my options?,Are there clinical trials for HP that I might be eligible for?,Do I need to change my job or home environment, and can you refer me to an occupational medicine specialist?,How often should I have breathing tests and imaging to monitor my lung health?
Common questions about Hypersensitivity pneumonitis
What is Hypersensitivity pneumonitis?
Hypersensitivity pneumonitis (HP), also called extrinsic allergic alveolitis (EAA), is a lung disease caused by the immune system overreacting to certain substances that are breathed in. When a person with HP is repeatedly exposed to triggers like mold, bird droppings, certain chemicals, or dust from hay or grain, their immune system attacks the lungs as if those substances were dangerous invaders. Over time, this causes inflammation deep inside the lungs. HP can be acute (coming on suddenly after a large exposure), subacute (building up over weeks), or chronic (developing slowly over months
How is Hypersensitivity pneumonitis inherited?
Hypersensitivity pneumonitis follows a multifactorial inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
Are there clinical trials for Hypersensitivity pneumonitis?
Yes — 9 recruiting clinical trials are currently listed for Hypersensitivity pneumonitis on UniteRare. See the clinical trials section on this page for phase, sponsor, and site details sourced from ClinicalTrials.gov.
Which specialists treat Hypersensitivity pneumonitis?
25 specialists and care centers treating Hypersensitivity pneumonitis are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.