Leoffler’s syndrome is a benign and transient pulonary involvement and a complex allergic reaction of the lungs which includes: perpheral blood eosinphilia, some manifestations as : fever, cough, dyspnea, or lac of any of these ; presence of one or more loci of consolidation on the chest film which are fleeting or migratory.

Loeffler’s syndrome any occur without any known cause, following parasitic infestation, or as a result of use of some drugs. In this article Loeffer’s syndrome is discussed in detail, an up to date and complete list of the drugs and chemicals which reported as occasional cause of the syndrome is presented . the pathogenesis of the various species of parasites causing this syndrome and other pulmonary involvement is mentioned. The role of eosinphils in inhibition of the parasitic infections is also discussed briefly.