May also be called: Hypersensitivity Pneumonitis, HP, Extrinsic Allergic Alveolitis, Bird Fancier’s Lung, Farmer’s Lung, Hot Tub Lung

Pneumonitis (noo-muh-NY-tus) is a general term for inflammation of the lungs.

More to Know

When someone has pneumonitis, it means that tiny air sacs in the lungs called alveoli have become irritated and swollen. Pneumonia — a type of lung infection — is technically one form of pneumonitis, but in general doctors use the term “pneumonitis” to describe illness caused by something that the person has inhaled. This can cause shortness of breath, a dry cough and other symptoms. Over time, if it goes untreated, pneumonitis can lead to lung damage and a condition called pulmonary fibrosis that can be life threatening.

Radiation treatments and certain drugs can cause pneumonitis, but much of the time people get pneumonitis from inhaling airborne dust containing certain types of fungus or molds. This is called hypersensitivity pneumonitis, and it’s most common in people who spend a lot of time around birds and people who work on farms and are exposed to dust from moldy hay and grain. For this reason, hypersensitivity pneumonitis is sometimes called “bird fancier’s lung” or “farmer’s lung.”

In many cases, people never know what caused them to get pneumonitis. In other cases, the cause can be obvious. Treatment for pneumonitis involves identifying the cause and then taking steps to avoid it. In chronic cases, which have been going on for a long time, doctors may prescribe medications to reduce inflammation in the lungs or fight infections.

Keep in Mind

In most cases, pneumonitis will clear up on its own if the cause can be identified and successfully avoided. Because long-term inflammation of the alveoli can lead to irreversible lung damage, ask a doctor about any lasting symptoms.

All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts.