My baby's full body skins redness iching allergy What we will do?

A. Red Colour Rash over the body if present could be some allergy rashes which may be of sudden onset along with itching. or it could be viral exanthematous rash where the the onset of rashes is there along with fever or assosiated symptoms. and it could be some infecftion also which needs proper examination. Application of calamine lotion or Anti itch lotion like Ritch lotifon can be done for soothing along with antiallergic medications initially.