A hypersensitivity pneumonitis caused by the repeated exposure and inhalation of biological dust (such as hay dust, mold spores, or other agricultural products). It is considered a type II hypersensitivity inflammatory reaction. In the acute phase, signs and symptoms include fever, chills, cough, dyspnea, headache, and chest tightness. The subacute phase manifests as chronic cough, dyspnea, anorexia, and weight loss. The chronic phase results from the prolonged exposure to the antigen and is characterized by severe dyspnea and irreversible damage to the lungs.