please advice on DD's rash

[nosleeptilbedtime]

DD (8 yearss old) came home from school yesterday with a rash that looked like hives, it went down and we forgot about it.
Today she has come home with an even worse rash all over, mainly face and arms.
Took her to gp this evening and she said that it looked like an allergic reaction.
This eve she had a dry cough (nothing serious) and fell asleep during her story (this never happens)
Gp was pretty unconcerned about her, but I am really worried.
Could there be something at school she is allergic to? It is not her lunch as she has packed lunches.
Also she had her MMR booster(we missed it out so were catching up) and that was just over 3 weeks ago. Doc was quite adament that it wasn't a reaction to that but I am not sure as she hasn't ever had a rash like this before and nothing in her environment has really changed.
Any help or advice much appriciated

bump for you - my ds (1) has a bad rash at the moment following a high fever which by my own research matches the description of rubella, but doctors say this is uncommon.

thanks blondissimo, she now has a v high temp too so I'm guessing it's not an allergy. Also a dry cough.
Have phoned gp and nhs direct but they have a 6 hour wait time due to swine flu

I know I tried nhs direct too but hung up and called GP instead. To be honest I think all they will say is to use calpol to keep the temp down and to keep her well hydrated.