Hi, My Son Is 3 Years And Having On And

Hi, my son is 3 years and having on and off fever since 3 days. no symtoms of cold or cough,just fever and it varies from 100 to 103 at night. Doc prescribed Dolonim 5 ml twice daily. but it helps only 4 to 5 hrs and again fever appears. another doc prescribed Imol. please suggest which medicine is better and do not have side effect. m very worried about this irregular fever.