Anyone ever heard of a virus causing a SEVERE Rash?

ok so yeserday morning when my 17 month old daughter woke up she had little red dots on her face and chest and a little on her back.. so i thought she was having an allergic reaction to her new Dora bath soap that she had used for the first time the night before so i made her a dr appt for the next day and spoke with a nurse who said if it got any worse to take her to the ER well when i got home from work at 7pm it was A LOT worse.. she is covered from head to toe literally in the worst "rash" i have ever seen.. but she isnt scratching so i took her to the ER where the doctor said it was NOT an allergic reaction that it is the "after affect" of a virus that she had last week.. so my question is has anyone else ever experienced a rash this severe from a virus? i just dont believe that this is the "after affect" of a virus.. also they gave me nothing for it.. no cream no benedryl, nothing.. then the nurse comes in and says oh well if it will make you feel better you can give her some benedryl.. so please some one tell me im not alone!!