Lung & Sleep Clinic

Types of Lung Disorders- Hypersensitivity Pneumonitis

Hypersensitivity pneumonitis is a disease in which your lungs become inflamed when you breathe in certain dusts to which you are allergic. These dusts contain fungus spores from moldy hay or the droppings of birds.

When you inhale this dust the first time, you won't notice any problem. But after repeated or intense exposure to the dust some people may develop symptoms. The tiny air sacs in the lung become inflamed, their walls fill with white blood cells, and sometimes the sacs fill with fluid. The disease may flare up again because of more exposure to the dusts. Parts of the lung may develop scar tissue and can no longer function normally in breathing.

How serious is Hypersensitivity Pneumonitis?

There is no cure or effective treatment for hypersensitivity pneumonitis. The good news is that the disease can be completely reversed in its early stages if you avoid the dust that causes it.

Lung scarring, or pulmonary fibrosis, may occur in the later stages of the disease. This damage is permanent and can occur even after symptoms have disappeared.

What Causes Hypersensitivity Pneumonitis?

The disease is caused by natural material that is inhaled as a fine dust. Allergy to the dust develops over a period of several months to a number of years.

The disease most often occurs in people who work in places with high levels of dust that contain fungus spores from mold. The most common type of hypersensitivity pneumonitis is farmer's lung, which can develop from exposure to moldy hay, straw and grain.

Hypersensivity pneumonitis can also develop from fungus in humidifiers, heating systems, and air conditioners found in homes and offices, especially if they are not well maintained. Exposure to certain bird droppings can also lead to hypersensitivity pneumonitis.

Other causes of hypersensitivity pneumonitis are dusts from:
  • Moldy sugar cane
  • Barley
  • Maple bark
  • Cork
  • Animal hair
  • Bird feathers and droppings
  • Mushroom compost
  • Coffee beans
  • Paprika

What are the Symptoms of Hypersensitivity Pneumonitis?

The symptoms of an attack are similar to those of the flu and appear some 4-6 hours after the person breathes the dust. They include:
  • Chills
  • Fever
  • Dry cough
  • Shortness of breath
  • Tight feeling in the chest
  • Tiredness
The symptoms may last for as little as 12 hours or as long as 10 days. Between attacks you may have no symptoms and feel quite normal.
After repeated exposure to the dust, these symptoms may occur:
  • Chronic cough with a lot of phlegm containing pus
  • Shortness of breath
  • Loss of appetite
  • Weight loss

How is Hypersensitivity Pneumonitis Detected?

Your doctor will take a careful, detailed medical history to match your dust exposure to your symptoms. Your doctor will also do a physical exam and listen to your lungs with a stethoscope. One sign of hypersensitivity pneumonitis is abnormal lung sounds called crackles.
Tests may include:
  • Blood tests
  • Tests of molds from your workplace
  • Chest x-ray
  • CT scan of the chest
  • Lung function tests
  • Challenge test, in which you inhale the materials to which you are sensitive to test your reaction
  • Lung biopsy

How is Hypersensitivity Pneumonitis Treated?

Avoiding the dust that causes the disease is the single most important thing you can do because in the early stages the disease is completely reversible.

Most drugs are not very effective in treatment. Antihistamines and bronchodilators do not work. Steroids can relieve the symptoms of attacks of hypersensitivity pneumonitis but do not cure the disease. Recovery from attacks may take as long as three weeks.

If you have the disease and are a smoker, now is the time to quit. Cigarette smoking may worsen symptoms of the disease. Smokers with hypersensitivity pneumonitis are likely to get complicating lung diseases, such as emphysema, chronic bronchitis, or lung cancer.

Preventing Hypersensitivity Pneumonitis

Properly drying and storing farm products can help prevent hypersensitivity pneumonitis. The fungus spores that cause farmer's lung grow only in moist conditions. Proper ventilation and using respiratory masks can also help prevent the condition.

If you begin to have symptoms of hypersensitivity pneumonitis from work exposure, the disease can be stopped if it is identified early enough. You can prevent permanent lung damage by stopping exposure to the dust. If control measures do not work or are not possible, you may have to change jobs.

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