I have viral fever- last 3 days.now fever etc is less but i have red rash on my arms & legs. skin very dry with intense itching.taking 4-5 ltrs fluids?

Viral rash: This sounds like a typical viral rash that can accompany viral infections and tends to manifest towards the end of the illness when the fever has started subsiding. Itchiness can accompany a viral rash and you can take simple antihistamines and soothing moisturising lotions for this. Keep up your fluid intake and stop all other medications if your fevers have subsided.

4-5 LITERS???: You do not need to drown yourself. "Viral fever" is so vague as to be a nearly useless diagnosis. Rash on arms and legs may---- or may not---- be viral. How do you know your fever is viral? You should at least apply a lubricating cream, and probably a cortisone cream. There is no point to excessive water consumption.