In case fever doesnt go away for a 5 years old with medication. is it ok to wash whole body with water or certain parts should be avoided?

Missing data: You get the most from your questions when you provide specific information that supports them. How much fever & for how long. Fever is a natural defense mechanism of the body that speeds the heart rate causing increased blood flow which brings healing factors fight illness. Fever by itself is not a problem. A cold bath can actually trigger shivering and increase fever.