Conditions with pulmonary fibrosis

Hypersensitivity pneumonitis

Hypersensitivity pneumonitis is a rare interstitial lung disease (ILD) that can cause a build-up of scarring in the lungs, also known as pulmonary fibrosis.¹

While hypersensitivity pneumonitis is quite rare, some people have a higher likelihood of developing it because of substances they are exposed to (eg, certain farmers and bird breeders). Hypersensitivity pneumonitis occurs when the body’s immune system overreacts in response to foreign substances, known as antigens or allergens, a person has breathed in.¹ When the symptoms of this condition do not go away, it is referred to as chronic hypersensitivity pneumonitis, or CHP.

Hypersensitivity pneumonitis

Possible antigens leading to hypersensitivity pneumonitis can include:

Infectious organisms in mouldy hay or contaminated hot tubs^1,2

Proteins from bird feathers or droppings^1,2

Tiny chemicals like those used in plastics manufacturing or certain types of spray paint³

These are just a few examples from hundreds of different substances where prolonged exposure can lead to inflammation in the lungs, known as pneumonitis.^1,2

Chronic hypersensitivity pneumonitis can lead to pulmonary fibrosis

After early exposure to an antigen, a person will often have fever and sore muscles/joints. Eventually they may develop cough and, less commonly, shortness of breath. These symptoms can go away if the person completely avoids the triggering antigen. This is known as acute hypersensitivity pneumonitis.¹

If the person has repeated exposure to the antigen, the symptoms won’t go away. This is known as chronic hypersensitivity pneumonitis (CHP),  and is often associated with pulmonary fibrosis (lung scarring) that makes it difficult to breathe.¹

Sometimes the antigen leading to chronic hypersensitivity pneumonitis isn’t identified. Other factors, such as some viral infections, medications, and genetics may increase the risk of chronic hypersensitivity pneumonitis. It is not yet established why some people get  chronic hypersensitivity pneumonitis and others don’t.²

Watch the video below to learn more about pulmonary fibrosis in hypersensitivity pneumonitis.

Symptoms of chronic hypersensitivity pneumonitis

There are a variety of symptoms you may experience with chronic hypersensitivity pneumonitis. These may be less obvious at first and gradually become more noticeable.^4,5 These symptoms include^2,5:

Dry cough

Shortness of breath, especially with mild physical activity

Feeling very tired when going about your normal day

Some individuals experience weight loss

These symptoms may arise from other causes, and do not necessarily mean you have chronic hypersensitivity pneumonitis, but keeping a diary of them may help you have a conversation with your healthcare professional if you're concerned.

Symptoms can also vary from one person to another, so your symptoms may not be the same as somebody else who has chronic hypersensitivity pneumonitis.² The earlier chronic hypersensitivity pneumonitis is diagnosed, the sooner you can get support and your doctor can decide the best way forward for you.^2,3

Talking to your healthcare professional about your symptoms

You and your healthcare professional may find it helpful to keep a record of any chronic hypersensitivity pneumonitis symptoms you may have been experiencing. Take note of:

Has anything changed in your work or home environment?
Do your symptoms get worse or better depending on where you are or what you are doing at the time?

How long do your symptoms last and how often do you experience them?
Could you be allergic to something?

Important

If your symptoms worsen suddenly, keep calm and alert someone nearby so they can contact your treatment team. If your symptoms are severe, you or someone close to you should contact the emergency services.

How is chronic hypersensitivity pneumonitis diagnosed?

When diagnosing chronic hypersensitivity pneumonitis, your treatment team will look at many areas of your health. For example, they will ask you about your home and work environment, family medical history, medications that you are taking, and whether you smoke or have ever smoked. A physical examination is also used to give the doctor a better understanding of your lung health. However, other tests, particularly breathing tests and X-rays or computed tomography (CT) scans, will be needed to make a clear diagnosis.²

Waiting for and receiving a diagnosis of chronic hypersensitivity pneumonitis can feel confusing and frustrating⁶; however, pushing for an early diagnosis and management of chronic hypersensitivity pneumonitis is important to give your lungs a chance of recovering.^2,3 Ask your doctor about your treatment options, including pulmonary rehabilitation, which could help you manage your condition.

Progression of chronic hypersensitivity pneumonitis

For some people with chronic hypersensitivity pneumonitis, symptoms may not fully resolve. Some people might face progression of the disease, which means over time, symptoms and how well your lungs work may get worse, or the high-resolution computed tomography (HRCT) scan may show that fibrosis in the lungs has increased.^2,4 However, currently there is no way of predicting if, or how fast, this will happen. Some people may not have changes in their symptoms, while others may experience a faster worsening of their symptoms. It is not known why the disease progresses more quickly in some people than others.^2,5

It’s important that your healthcare professional checks your lung health regularly so that any changes can be managed quickly.

Managing chronic hypersensitivity pneumonitis

Keeping your home and work environment well-ventilated can help keep the air clean and reduce dampness. This is important, because dampness can create an environment for mould to grow, which can trigger allergic reactions.⁷

Ask a loved one or employer to help limit your exposure to certain dusts both at home and in your workplace⁷:

Remove any standing water inside and outside of your home, as bacteria and fungus can thrive there
Reduce humidity in your home and workplace below 50%
Properly maintain heating, ventilation, and air conditioning systems

Repair any water damage at home or at work, including carpets, furniture, and drywall
Properly dry and store any farm products you work with

Ask your treatment team for guidance on how to speak with your employer about changes you may need to make to your workplace.

Managing life with hypersensitivity pneumonitis

Receiving a diagnosis of hypersensitivity pneumonitis can feel lonely and uncertain; at these times it can feel very difficult to stay positive. Daily life can be challenging, both practically and emotionally. However, there are many strategies to help people living with pulmonary fibrosis.

Abbreviations: CHP, Chronic hypersensitivity pneumonitis; CT, computed tomography; HP, Hypersensitivity pneumonitis; HRCT, high-resolution computed tomography; ILD, interstitial lung disease; IPF, idiopathic pulmonary fibrosis; PF, pulmonary fibrosis; RA, Rheumatoid arthritis; RA-ILD, rheumatoid arthritis-associated interstitial lung disease.

Asthma + Lung UK. Pulmonary fibrosis: hypersensitivity pneumonitis. Updated June 1, 2022. Accessed October 2, 2024. https://www.asthmaandlung.org.uk/conditions/pulmonary-fibrosis/hypersensitivity-pneumonitis
National Heart, Lung, and Blood Institute. What are interstitial lung diseases? Updated March 24, 2022. Accessed October 1, 2024. https://www.nhlbi.nih.gov/health-topics/hypersensitivity-pneumonitis
Riario Sforza GG, Marinou A. Hypersensitivity pneumonitis: a complex lung disease. Clin Mol Allergy. 2017;15:6.
Vasakova M, Morell F, Walsh S, Leslie K, Raghu G. Hypersensitivity pneumonitis: perspectives in diagnosis and management. Am J Respir Crit Care Med. 2017;196(6):680-689.
Salisbury ML, Myers JL, Belloli EA, Kazerooni EA, Martinez FJ, Flaherty KR. Diagnosis and treatment of fibrotic hypersensitivity pneumonia. Where we stand and where we need to go. Am J Respir Crit Care Med. 2017;196(6):690-699.
Aronson KI, Hayward BJ, Robbins L, et al. ‘It’s difficult, it’s life changing what happens to you’ patient perspective on life with chronic hypersensitivity pneumonitis: a qualitative study. BMJ Open Resp Res. 2019;6:e000522.
American Lung Association. Treating and managing hypersensitivity pneumonitis. Updated June 7, 2024. Accessed October 2, 2024. https://www.lung.org/lung-health-diseases/lung-disease-lookup/hypersensitivity-pneumonitis/treating-and-managing