The investigation of eosinophilia

Eosinophilia is a common problem in returning travellers and migrants. It is frequently asymptomatic, but still deserves geographically directed investigation to prevent significant disease in the future. The presentation may differ between those who have migrated from endemic areas - who can have heavy infections with a subacute course - and travellers, in whom acute presentations are usual. Negative tests should be repeated if they were performed within 3 months of return from the tropics. Although eosinophilia in travellers returning from the tropics is usually caused by helminth infection, it is important to bear in mind the possibility of a non-infectious cause.