HealthSheets™


Understanding Hypersensitivity Pneumonitis

Hypersensitivity pneumonitis is lung inflammation caused by inhaling allergens in your environment. Allergens may be things such as molds, fungus, bacteria, dust, or chemicals. Exposure to the allergens triggers the immune system, which leads to inflammation. This can make it hard to breathe. It can also cause permanent lung damage. Recognizing allergens and treating this condition early can reverse the inflammation in the lungs and help prevent permanent lung damage or other long-term problems.

What causes hypersensitivity pneumonitis?

Hypersensitivity pneumonitis is caused by repeated and prolonged exposure to allergens in the environment. Exposure often occurs at home or in the workplace. But not everyone exposed to these substances gets hypersensitivity pneumonitis.

Front view of man's head and chest showing allergens being breathed into lungs.

Allergens include:

  • Bacteria

  • Mold

  • Fungi

  • Chemicals

  • Proteins

These allergens can be found in the environment in things such as:

  • Farming, vegetable, and dairy cattle workers

  • Bird and poultry handlers

  • Animal handlers and veterinarians

  • Grain and flour processors

  • Lumber and construction workers

  • Workers in plastics and electronics industries

  • Textile workers

Symptoms of hypersensitivity pneumonitis

Symptoms can develop 4 to 6 hours after exposure. But, it can take several months to years to develop an allergy to the substance. Early symptoms are flu-like and include:

  • Trouble breathing and shortness of breath

  • Cough

  • Tight chest

  • Fever

  • Chills

  • Tiredness

  • Muscle aches

Later symptoms include weight loss, chronic bronchitis, signs of lung scarring, and clubbing of fingertips or toes.

Treatment for hypersensitivity pneumonitis

This disease can be completely reversible if diagnosed or found in its early stages. Ideally, you should stay away from the dust or allergen. If you can’t do that, ask your healthcare provider about wearing a respirator.

Your healthcare provider may prescribe:

  • Steroids to reduce inflammation

  • Immune suppressing medicines

  • Oxygen therapy

  • Bronchodilators to relax the airways

Possible complications of hypersensitivity pneumonitis

If this condition is not treated, you can develop:

  • Permanent lung scarring (pulmonary fibrosis)

  • High blood pressure in the lung arteries (pulmonary hypertension)

  • Heart failure

Living with hypersensitivity pneumonitis

Once diagnosed with hypersensitivity pneumonitis, it’s key to avoid the substance that is irritating your lungs. These steps can help reduce the inflammation in the lung that can lead to permanent scarring:

  • Be sure to have any standing water inside or outside your home removed.

  • Keep humidity inside your home or workplace below 60%.

  • Have your air conditioning and heating systems checked regularly.

  • Have any water damage in your home repaired as soon as possible.

Other important lifestyle steps include:

  • Quit smoking. Some studies suggest smoking can make the disease worse.

  • Stay on top of your mental health. Having a chronic disease can take its toll without good support.

  • Keep up-to-date on vaccines, including a yearly flu shot and pneumococcal vaccine.

  • Get regular physical activity with your doctor’s OK.

When to call your healthcare provider

Call your healthcare provider right away if you have any of these:

  • Fever of 100.4°F (38°C) or higher, or as directed by your provider

  • Chills

  • Chest tightness

  • Cough

  • Shortness of breath

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