17898 Hypersensitivity Pneumonitis

Overview

Hypersensitivity pneumonitis (often called HP) is a lung condition caused by inhaling tiny particles of dust, mold, or animal proteins again and again. It is not an infection. Instead, your immune system overreacts to these particles, causing inflammation in the air sacs of your lungs.

Hypersensitivity pneumonitis is not very common. It is often linked to specific jobs, hobbies, or homes where people are exposed to certain dusts regularly.

It can affect anyone at any age, but it is more often seen in adults who work around contaminated air — such as farmers, bird keepers, or people in certain industries. Non-smokers and people who have repeated exposure are more at risk.

Symptoms

Common symptoms

• Shortness of breath
• Dry cough that doesn't go away
• Feeling tired and weak
• Fever or chills shortly after exposure
• Tightness in the chest
• Weight loss in long-term cases

Symptoms in children

• Children can have the same symptoms, plus poor weight gain, fussiness, and low energy. They may not be able to explain their breathing discomfort, so look for fast breathing, wheezing, or frequent coughs.

Symptoms in older adults

• In older adults, symptoms may be mistaken for aging or other lung problems. Look for gradual fatigue, shortness of breath during daily activities, and a dry cough. Any new breathing trouble should be checked by a doctor.

Causes

Main causes

• Inhaling moldy hay, straw, or grain (sometimes called 'farmer's lung')
• Breathing in particles from bird feathers, droppings, or down (called 'bird fancier's lung')
• Contaminated humidifiers, air conditioners, or water heaters
• Exposure to certain chemicals or metal dusts at work

Risk factors

• Working on a farm or with livestock
• Keeping birds as pets or working in a bird-rich environment
• Living in a home with water damage, mold, or poor ventilation
• Having a hobby like woodworking, gardening, or making compost that stirs up dust
• A family history of allergies or autoimmune conditions

When to see a doctor

See a doctor urgently if:

• Seek urgent care if you have new shortness of breath, a high fever, or a cough that is getting worse, especially if you know you were around mold or birds.

Book a routine appointment if:

• Make a routine appointment if you have had a dry cough or breathlessness for more than a few weeks, or if you keep getting tired after starting a new job or hobby.

Diagnosis

A doctor will listen to your history, ask about your home and work surroundings, and order tests to see how your lungs are working.

Tests that may be done

• Chest X-ray or CT scan to look for swelling or scarring in the lungs
• Lung function tests (breathing tests) to measure how well your lungs move air
• Blood tests to check for signs of inflammation or antibodies to common triggers
• Sometimes a sample of fluid from the lungs (bronchoscopy) is taken for closer examination

What to expect at your appointment

The process can take several visits. The doctor may ask you to keep a diary of your symptoms and where they happen. You may be referred to a lung specialist to confirm the diagnosis and make a treatment plan.

Treatment

The most important step is to remove the trigger from your life. Once you stop breathing in the dust or protein, your symptoms often improve. Medication can help reduce inflammation in more serious cases.

Self-care at home

• Stay away from the place or substances that cause the reaction
• If you cannot avoid exposure, wear a properly fitted respirator mask
• Keep your home well-ventilated and fix any water leaks or mold promptly
• Rest and drink plenty of fluids when symptoms are acute

Medical treatments

Doctors may prescribe medicines that reduce inflammation in the lungs, such as corticosteroids (these are only taken under close medical supervision). For people with severe or ongoing symptoms, other treatments that calm the immune system may be considered. If oxygen or lung rehabilitation is needed, your healthcare team will explain how to do this.

When is surgery considered?

Hypersensitivity pneumonitis is rarely treated with surgery. In extreme, advanced cases where the lungs are badly scarred, a lung transplant may be considered as a last resort by a specialist team.

Living with this condition

Learn to recognize what makes your breathing worse and keep a simple summary of your triggers. It can help to tell your employer, family, and friends so they can support you in reducing exposure.

Lifestyle tips

• Avoid damp, moldy areas and ask someone else to clean them if possible
• Change furnace or air conditioner filters regularly
• Wash or replace dusty bedding, carpets, and drapes if you have birds or mold
• If you keep birds, use a mask when cleaning their cages and keep birds outside if possible

Diet and exercise

Eat a balanced diet to keep your lungs strong, and stay active with exercises like walking or breathing exercises that your doctor advises. If your breathing is limited, a pulmonary rehab program can help you build fitness safely.

Mental health and emotional wellbeing

Living with a lung condition can feel stressful and worrying. Talk to your doctor if you feel anxious or low. Counseling or talking therapies can help, and support groups let you connect with others who understand.

Prevention

You can lower your chance of developing hypersensitivity pneumonitis by reducing exposure to known triggers. This means controlling moisture, improving ventilation, and wearing protection when working with dusts or birds.

Vaccines

Keep your routine vaccinations up to date, including the flu vaccine, to help protect your lungs from extra infections. Speak to your doctor or pharmacist.

Screening programmes

There is no routine screening for the general population, but if you have a high-risk job or hobby, your doctor may recommend regular breathing tests.

Complications

If left untreated

• Scarring of the lungs over time (pulmonary fibrosis)
• Permanent shortness of breath
• Low oxygen levels in the blood
• Increased risk of serious lung infections

Long-term outlook

With early diagnosis, most people improve when they avoid the cause. Some people may have permanent changes in their lungs, but treatment can still help them breathe comfortably and stay active. Your doctor will help you manage it step by step.

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