Abstract
Hypersensitivity pneumonitis (HP) is the excessive immune response in the lung parenchyma (alveoli, terminal bronchiole, interstitium), resulting from repeated exposure to a variety of antigens. From the clinical point of view, HP can be divided into acute, subacute, or chronic forms. Only few of the exposed individuals develop HP, but workers in environments contaminated by organic dust are at a higher risk. The pathogenesis of HP is complex and still under investigation. Previous research suggests that both type III and IV hypersensitivity reactions are involved. The main treatment is the removal of antigen. Therefore, research of causative agents and pathogenesis is of outstanding importance not only for early diagnosis but also the better treatment of HP.