How To Treat Skin Rashes In Kids?

My 1.6 old son has a rashes on cheeks and also on head .., especially he keeps scrating all over faces and head more at night time, b'coz of this he doesnt sleep properly, Prior to this one week back he had fever cold and cough now it has come down but the rashes still appear can you pls help to overcome the itchy during the night.