<unk>  <unk>  can be categorized as acute, subacute, and chronic based on the duration of the illness. Acute In the acute form of<unk>  dose of antigen exposure tends to be very high but only for a short duration. Symptoms may develop 4–6 hours following heavy exposure to the provoking antigen. Symptoms include fever, chills, malaise, cough, chest tightness, dyspnea, rash, swelling and headache. Symptoms resolve within 12 hours to several days upon cessation of exposure. Subacute Patients with subacute<unk>  gradually develop a productive cough, dyspnea, fatigue, anorexia, weight loss, and pleurisy. Symptoms are similar to the acute form of the disease, but are less severe and last longer. Findings may be present in patients who have experienced repeated acute attacks. Chronic In chronic<unk> , dose of the antigen tends to be low volume but for a longer duration. Patients often lack a history of acute episodes. They have an insidious onset of cough, progressive dyspnea, fatigue, and weight loss. This is associated with partial to complete but gradual reversibility. Avoiding any further exposure is recommended. Clubbing is observed in 50% of patients. Tachypnea, respiratory distress, and inspiratory crackles over lower lung fields often are present. In fact,<unk>  can often resemble (IPF) in terms of pulmonary fibrosis and that many patients experience hypoxemia.
Hypersensitivity pneumonitis
Idiopathic pulmonary fibrosis
Chemical pneumonitis
Acute eosinophilic pneumonia
Diffuse panbronchiolitis
Cryptogenic organizing pneumonia
Atypical pneumonia
Eosinophilic pneumonia