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Rare lung & airway condition

Hypersensitivity pneumonitis

Hypersensitivity pneumonitis is lung inflammation caused by an immune reaction to inhaled organic material - classically from birds, mould or damp - and finding and removing the trigger is the cornerstone of treatment.

Key points

The essentials at a glance.

What to look out for, how the diagnosis is confirmed, who looks after it, and the options that exist.

  • 01

    Sources include pet or wild birds and feather bedding, mould from damp buildings or hay, humidifiers, hot tubs and some workplace exposures.

  • 02

    Non-fibrotic disease often improves substantially once exposure stops; fibrotic disease behaves more like progressive scarring.

  • 03

    Diagnosis combines exposure history, high-resolution CT, bronchoalveolar lavage and sometimes biopsy - agreed at a specialist ILD MDT.

  • 04

    Blood tests for specific antibodies support, but do not prove, the diagnosis.

  • 05

    Treatment: strict antigen avoidance, steroids or immunosuppression for inflammatory disease, and nintedanib where fibrosis progresses despite this.

Understanding it

What it is, and what happens next.

In plain English - what is going on, how specialists confirm it, and the routes to treatment in the UK.

In hypersensitivity pneumonitis, repeated inhalation of a protein the immune system has learnt to hate - avian bloom from a pet parrot, mould spores from a damp wall or hay barn - inflames the small airways and air sacs. Caught early, it is one of the most reversible interstitial lung diseases; missed, chronic exposure drives fibrosis that no longer needs the antigen to progress.

The detective work is decisive, so assessment belongs with a specialist ILD team who take a forensic exposure history, arrange CT and lavage, and present the case at the MDT; management then pairs uncompromising removal of the source - including feather duvets and problem buildings - with immunosuppression for active inflammation and antifibrotic therapy for the progressive fibrotic minority. In many parts of the UK, routine NHS outpatient referrals for problems like this can take several months, whereas an initial appointment with a private consultant is typically available within around two weeks.

A quiet reminder

This guide is for information, not medical advice.

Your GP or specialist knows your history and can tell you which parts apply to you. If in doubt, speak to them.

Published 2026-09-27 · Next review 2027-09-27

Frequently asked

Common questions about Hypersensitivity pneumonitis.

Quick, plain-English answers to what people ask us most.

  • What does Hypersensitivity pneumonitis mean?

    Hypersensitivity pneumonitis is a health condition that affects how part of the body functions, and can range in severity from mild to significant depending on the individual. A clinician can assess your specific situation and explain what it means for you. Understanding the basics helps you ask the right questions at your appointment.

  • What causes hypersensitivity pneumonitis?

    There are usually several contributing factors behind hypersensitivity pneumonitis, and it's not always possible to pin down a single cause without proper assessment. Your doctor will consider your symptoms, history, and any relevant investigations to build a clearer picture. This helps make sure treatment is targeted appropriately.

  • What does hypersensitivity pneumonitis feel like?

    Symptoms can vary from mild and barely noticeable to more significant and disruptive, depending on severity and individual factors. Common features often include changes that affect comfort, function, or general wellbeing in the affected area or system. If you're experiencing symptoms that concern you, it's worth having them assessed rather than guessing.

  • How worried should I be about hypersensitivity pneumonitis?

    Most cases can be managed effectively once properly assessed and treated, though how serious it is depends on individual circumstances and how early it's picked up. Getting a professional opinion helps rule out anything more concerning and puts your mind at ease either way. Don't hesitate to seek advice if something feels wrong.

  • Is hypersensitivity pneumonitis hereditary or genetic?

    Some cases have a genetic or family component, while others are linked more to lifestyle, environment, or other health conditions. Having a family history may increase your risk slightly, but it doesn't mean you'll definitely develop it. A clinician can advise whether genetic factors seem relevant in your particular case.

  • Can hypersensitivity pneumonitis be prevented?

    Treatment can often reduce symptoms significantly and, in some cases, resolve the underlying problem entirely, though this isn't guaranteed for everyone. Prevention strategies, where they exist, usually focus on managing risk factors and general health. A tailored discussion with your doctor will give you the clearest picture for your circumstances.

  • How is hypersensitivity pneumonitis treated?

    Treatment options range from conservative measures such as lifestyle changes, medication, or physiotherapy through to more involved interventions in more severe or persistent cases. The right approach depends on the underlying cause, severity, and how it's affecting you. Your specialist will talk through the pros and cons of each option that's relevant to you.

  • What is the typical recovery time for hypersensitivity pneumonitis?

    Some people recover within a matter of weeks, while others find it becomes a longer-term or recurring issue that needs ongoing management. Following your treatment plan closely tends to support the best possible recovery. Ask your specialist for a realistic timeline based on your own results and progress.

  • When is a specialist opinion or surgery needed for hypersensitivity pneumonitis?

    A specialist opinion is generally recommended if symptoms persist despite initial treatment, if they're severe, or if there's uncertainty about the diagnosis. Surgery or more invasive treatment is usually reserved for cases where conservative measures haven't worked. Your GP can refer you on if they feel a specialist review would be helpful.

  • When is it worth getting hypersensitivity pneumonitis checked by a specialist?

    See a doctor if symptoms are persistent, worsening, or affecting your daily life, or sooner if you have any red-flag symptoms your GP has warned you about. NHS routine referrals for this can take anywhere from around 20 to 45+ weeks depending on your local waiting list, while most private consultants can offer an initial appointment within about 2 weeks.