What Is The Cause Of Vomiting, Diarrhea And Rashes In A Child?

My 10 year old daughter woke up this morning vomiting also with diarrhea. She is feeling better now, no fever, but now she has a rash on her torso and the back of her upper arms. They are pencil eraser sized red spots that are slightly raised. She said they do not itch, but the midline of her chest did itch. One of the spots on the back of her arm is nickel size and has a tan colored scab. Just wondering what could be causing this?