My 6 year son from last 3 years after 2 or 3 month...

Treatment of high body tempreature 
fever is a sign of an underlying etiology which is in most of cases a clue of a viral infection but it may be due to other causes which we will mention later.
fever is classified according to its deverity in to high grde (above 38.4) and low grade below this reading, so once a patient has a fever he should be checked for the underlying cause and to treat this increase in body tempreatures using cold compress over groins, behind the knee and armpits in addition to the use of antipyretics named Paracetamol Syrup in a dose of 10 cm orally that could be repeated every 6 hrs. 
If your childs fever perisited beyond 48 hrs or if it was high fever it should be investigated and your child examined by your treating family doctor.
Required investigations 
To start investigating high body tempreature your child should be examined for the common causes of fever by throat, ear, chest exam by a doctor, to aid in identifying the underlying cause Complete blood count is advisable to detect any increase in white cell count , other lab incestigations will include ESR , thoat ASOT testing , urine analysis and chest X Ray. 

Causes of high body tempreature 

• Viral infections ( acute bronchitis, sore throat , Common cold)
• Bacterial infections ( tonsillitis , pharyngitis , ear infections , Pneumonia, UTI)
• Rheumatologic diseases ( Jouvenile rhematoid arthritis ,kawazaki disease) 
• other rare cause might be anticipated like blood leukemias 

Advices
you are adviced to monitor your child's  response to treatment to avoid febrile convulsions that happen with high body tempreature , at the same time encourage your child to drink warm drinks and assure he is feeding properly healthy daily diet and if his general conditions is worrying dont hesitate to contact your family doctor .