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Health condition

Hypersensitivity pneumonitis

Hypersensitivity pneumonitis is lung inflammation caused by an inhaled organic trigger - bird proteins, moulds, humidifier microbes - and identifying and removing the exposure is the single most important treatment step.

Why trust this guide

  • 01

    Editorial team

    Written by our editorial team from the UK sources listed on each page.

  • 02

    Sourced from guidance

    Checked against current NHS and UK specialist society guidance at the time of review.

  • 03

    Current for 2026

    Reviewed on 2026-09-27 with the next review scheduled for 2027-09-27.

Key facts

The essentials at a glance.

The symptoms to recognise, when to seek help, which specialist to see, and what treatment usually involves.

  • Classic culprits: pet birds and pigeon lofts, mouldy hay (farmer's lung), humidifiers and hot tubs, and contaminated ventilation

  • Acute form: flu-like symptoms with cough and breathlessness hours after a heavy exposure; chronic form: insidious breathlessness and weight loss that mimics pulmonary fibrosis

  • The exposure history is the diagnostic key - the connection is often missed for years because symptoms lag behind exposure

  • Specialist: an ILD-specialist respiratory physician; antigen avoidance, steroids for significant inflammation, and antifibrotics for progressive scarring form the treatment ladder

Understanding the condition

What it is and what happens next.

What causes it, how it is diagnosed, and the treatment routes available in the UK.

What it is and how it feels

In susceptible people, repeatedly inhaled organic particles provoke an immune reaction deep in the lung, inflaming the air sacs and small airways: the acute version brings drenching flu-like episodes hours after mucking out the loft or opening the mouldy bales, while the more treacherous chronic version builds silently under continuous low-level exposure - the beloved cockatiel in the lounge, the damp bedroom wall - producing creeping breathlessness, cough and fatigue that eventually earns a fibrosis-like scan. The tragedy of late diagnosis is that early disease is substantially reversible, while established scarring is not; and the diagnosis hinges on someone taking a forensic exposure history connecting home, hobbies and work to the lungs.

Diagnosis and treatment routes

Investigation combines high-resolution CT (showing characteristic inflammatory patterns), blood tests for antibodies against candidate antigens, bronchoscopy with lavage showing the typical immune cell profile, and multidisciplinary review - but no test substitutes for the environmental audit, and a home visit or detailed questionnaire sometimes finds what clinic conversations missed. Treatment begins with rigorous, complete antigen avoidance, which alone can arrest and reverse early disease (half-measures with the birds rehomed but the feather duvet retained genuinely fail); corticosteroids accelerate recovery in significant inflammation, and for the chronic fibrotic form that continues progressing despite avoidance, antifibrotic medication now has an evidence base. In many parts of the UK, routine NHS referrals for this kind of problem currently take 20-45+ weeks, whereas an initial appointment with a private consultant is typically available within around two weeks.

Seeing a specialist

Who to see, and how quickly you can be seen.

The specialist for this condition is usually a consultant respiratory physician specialising in interstitial lung disease. Your GP can refer you on the NHS, or you can arrange a private consultation directly.

A quiet reminder

This guide is for information, not medical advice.

Your GP knows your history and can tell you which parts apply to you. If in doubt, see them - and seek urgent care for any of the emergency symptoms described above.

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.