sentences:  Diffuse alveolar damage (DAD) can occur with acute respiratory failure; progressive interstitial fibrosis is typical of the chronic form.In both, the underlying inflammatory response stops upon exclusion of the allergen, but symptoms may persist depending on the degree of damage already sustained.Among invasive procedures, bronchoalveolar lavage typically shows prominent lymphocytosis with an inverted CD4+/CD8+ ratio, and lung biopsy usually reveals non-necrotizing granulomatous inflammation.