Schistosomiasis is a tropical helminthic infection, observed in travelers as well as local populations. It is most often due to Schistosoma mansoni or Schistosoma haematobium and can be diagnosed at the invasive phase. Migration of the schistosomulae (larvae) in the body leads to acute parasitic toxemia, which includes a hypersensitivity reaction and circulating immune complexes. The invasive stage occurs generally 2 to 6 weeks after the exposure and combines fever, asthenia, faintness and headaches. Other signs include diarrhea, dry cough, dyspnea, urticarial rash, arthralgia, myalgia, and enlargement of liver and spleen. Although rare, neurological and cardiac complications may be fatal. This diagnosis should be considered in travelers returning from the tropics with compatible clinical signs and delayed hypereosinophilia, if they report exposure in an endemic area. It is later confirmed by seroconversion for schistosomiasis and then by observation of schistosome eggs in stool or urine (according to species). The standard treatment of acute schistosomiasis with praziquantel is ineffective and can aggravate clinical outcome during this phase. Corticosteroid treatment is recommended for serious forms with neurological or cardiac manifestations.