dear user thanks for contact HCM first you need not to get worried of that about your question of fever along with vomiting and rashes i would like to tell you that we have to illustrate that as follow.......you may have viral infection or bacterial ..... first you may have immunological and allergic reaction following viral infection as immune reaction appear as red rashes and it is common following viral infection and no worry of that.....you may have administered medications that enhance allergic reactions and red rashes is main sign of this allergy .................you need not to worry ....just simple investigations and you will be fine.. you nedd to do stool culture and blood culture and urine analysis to detevt the causative micro organism ..... wish you healthy life