Hypersensitivity pneumonitis is caused by repeated exposure to environmental substances that cause inflammation in the lungs when inhaled. These substances include certain:
- Bacteria and mycobacteria
- Fungi or molds
Learn more about common environmental sources of substances that may cause your condition.
Where can these substances be found in the environment?
Common environmental sources of substances that can cause hypersensitivity pneumonitis are:
- Animal furs
- Air conditioner, humidifier, and ventilation systems
- Bird droppings and feathers
- Contaminated foods such as cheese, grapes, barley, sugarcane
- Contaminated industry products or materials such as sausage casings and corks
- Contaminated metal working fluid
- Hardwood dusts
- Hay or grain animal feed
- Hot tubs
Because this condition is caused by different substances found in many environmental sources, doctors once thought they were treating different lung diseases. Research has helped us understand hypersensitivity pneumonitis is triggered by different causative substances.
Why does hypersensitivity pneumonitis only occur in some people?
If you have hypersensitivity pneumonitis, your body’s immune system reacts strongly to certain substances. Differences in our immune systems may explain why some people have strong reactions after breathing in certain substances, while others who breathe those same substances do not.
Learn more about the immune system of the lungs and how it contributes to hypersensitivity pneumonitis.
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Normally, the immune system in the lungs monitors inhaled substances. The immune system is activated when it recognizes a portion of the substance called theas foreign. The activated immune system produces molecules that cause normal levels of inflammation, such as increased levels of immune cells and factors including antibodies that recognize and help clear the foreign substance. Normally after clearing the substance, the immune system shuts off and the inflammation stops. Usually, these processes are well controlled.
The immune systems of people with hypersensitivity pneumonitis are unable to shut down these normal inflammation processes, especially in the signs, symptoms, and complications of this condition.. The interstitium is a space where the lung’s air sacs, called alveoli, come in contact with blood vessels and a small amount of connective tissue. When there is high level of inflammation in the lungs, immune cells begin to collect in this space. These uncontrolled levels of inflammation in the lungs cause the