Understanding Hypersensitivity Pneumonitis

What is 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


Learn more about the Symptoms, Diagnosis and Treatment of Hypersensitivity Pneumonitis