(See also Overview of Interstitial Lung Disease Overview of Interstitial Lung Disease Interstitial lung diseases are a heterogeneous group of disorders characterized by alveolar septal thickening, fibroblast proliferation, collagen deposition, and, if the process remains unchecked... read more .)
Parasitic infections, especially ascariasis Ascariasis Ascariasis is infection with Ascaris lumbricoides or occasionally Ascaris suum (a closely related parasite of pigs). Light infections may be asymptomatic. Early symptoms are pulmonary... read more 
, may be the cause, but an identifiable etiologic agent is not found in up to one third of patients.
The diagnosis of Löffler syndrome is based on characteristic and often transient respiratory symptoms, chest x-ray findings, and peripheral blood eosinophilia. It requires the exclusion of other types of eosinophilic lung disease. For example, acute eosinophilic pneumonia Acute Eosinophilic Pneumonia Acute eosinophilic pneumonia (AEP) is a disorder of unknown etiology characterized by rapid eosinophilic infiltration of the lung interstitium. (See also Overview of Eosinophilic Pulmonary Diseases... read more is a distinct entity with acute onset, severe hypoxemia, and typically a lack of increased blood eosinophils at the onset of disease.
The disease usually resolves within 1 month.
Treatment of Löffler syndrome is symptomatic and may consist of corticosteroids.
