Hypersensitivity pneumonitis
![](/Images/godic/202412/18/Histology_of_chronic_hypersensitivity_pneumonitis1312.jpg")
![Low magnification view of the histology of chronic hypersensitivity pneumonitis. The interstitium is expanded by a chronic inflammatory infiltrate. Two multinucleated giant cells can be seen within the interstitium at left, and a plug of organizing pneumonia at bottom left.](/Images/godic/202412/18/Chronic_hypersensitivity_pneumonitis_-_histology1313.jpg")
Hypersensitivity pneumonitis (HP; also called allergic alveolitis or extrinsic allergic alveolitis, EAA) is an inflammation of the alveoli within the lung caused by hypersensitivity to inhaled organic dusts. Sufferers are commonly exposed to the dust by their occupation or hobbies.