“…There is no agreed definition of OHP; it is loosely defined as a complex delayed hypersensitivity reaction with varying intensity, clinical presentation and natural history (Khalfey, 2015). It is a result of immunologically mediated inflammation of the lung parenchyma i.e., alveoli and surrounding interstitial tissues (Lacasse, Girard and Cromier, 2012;Quirce et al, 2016).…”