Hi dear, I understand your concern A sudden onset high grade fever along with rash is most likely a viral illness. If he do not have any other symptoms, is playful when fever comes down, and taking feeds, just give him paracetamol 3-4 times a day. Let him take rest and drink plenty of fluids. If the rash is itchy, apply calamine lotion over there 2-3 times a day. If bothersome, I used to give antihistamines like hydroxyzine or levocetirizine to relieve the itching. If he is not getting better in 2-3 days, or becomes lethargic or not at all taking feeds, kindly take him to doctor. Hope I have answered your query Let me know if I can assist you further Dr Muhammed Aslam, Paediatrician