Hypersensitivity granulomatous pneumonitis caused by the inhalation of avian antigens that are present in the dust of the droppings and feathers of many species of birds. in the acute phase it manifests as fever, chills, dyspnea, cough, and chest tightness. chronic exposure may lead to interstitial lung fibrosis.

Bird fancier's lung (BFL), also known as bird breeder's lung, is a type of hypersensitivity pneumonitis. It can cause shortness of breath, fever, dry cough, chest pain, anorexia and weight loss, fatigue, and progressive pulmonary fibrosis (the most serious complication)...