Extrinsic Allergic Alveolitis

**Semantic type:** Disease or Syndrome

**Definition:** An inflammatory interstitial lung disease caused by hypersensitivity reaction to inhalation or ingestion of antigens. The antigens are usually related to the patient's occupation. It can present as an acute illness with flu-like symptoms, subacute with repeated episodes of pneumonia, or chronic with dyspnea and productive cough. The majority of patients recover following the cessation of the exposure to the antigen that causes the disease. Chronic exposure may eventually progress to interstitial lung fibrosis.

**Synonyms:** - Allergic Pneumonitis - Hypersensitivity Pneumonitis