Hand foot and mouth!!

Okay help me please. a child i babysit is 1year old and her parents just found out she has hand foot and mouth disease. Ugh...so anyways my son is 4moths old and the er doctor told them that since my son has already been exsposed to her with a fever (when its contagious) that my son will have it and i shouldnt be alarmed or take him to the doctors? Is that normal? When he starts showing signs i dont even take him in? Also how do you treat this at home? Ive never had to deal witbthis. Thanks so much!