Hi,
See, what exactly it is, is something that the doctor will be able to tell because there can be rashes due to number of reasons, and other than the doctor it will be very difficult to tell this rash can be a virus, chicken pox or caused by some allergy etc. I suggest you take the baby to the paediatrician and see how he guides you through.
Also, there is a very good article in the link below with pictures, and you can read it and se if any of the explanation here matches with what your child is going through. Do not try giving any medication without consulting the doctor, but by reading this article atleast you will be at peace that there is nothing to worry about, and you can relax mentally.
http://thesurvivaldoctor.com/2012/06/26/fever-and-rashes-in-children/
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