• A high index of suspicion is key to the diagnosis of HP; antigen avoidance is the definitive therapy. • Allergic bronchopulmonary aspergillosis (ABPA) should be considered in poorly controlled asthmatics with peripheral eosinophilia. • A detailed review of the medication list and travel to endemic areas is essential to the diagnosis and treatment of eosinophilic lung diseases. • Bronchoalveolar lavage (BAL) aids to the diagnosis of acute and chronic eosinophilic pneumonias; both processes are steroid responsive. • Significant extrapulmonary organ involvement should raise suspicion for eosinophilic granulomatosis with polyangiitis (EGPA) and hypereosinophilic syndromes (HES). Hypersensitivity pneumonitis (HP) is traditionally classified into acute, subacute and chronic forms. A high index of suspicion and a detailed investigation into the patient's environment is the key to diagnosis and treatment of HP. Eosinophilic lung diseases can be broadly categorized as idiopathic (acute eosinophilic pneumonia, chronic eosinophilic pneumonia, eosinophilic granulomatosis with polyangiitis and hypereosinophilic syndromes), those with known cause (allergic bronchopulmonary aspergillosis, drugs, parasitic and non-parasitic infections), and those associated with other known lung diseases (asthma, interstitial lung diseases and lung cancers). A detailed review of drug intake, toxin exposures, and travel history is essential in the differential diagnosis of eosinophilic lung diseases. [ABSTRACT FROM AUTHOR]