7 yr. old had sore throat with low grade fever (100.2) for 48 hours. now a raised red rash started on legs and spread to arms, hands, face. causes?

Many possibilities: It could be viral (possibly even hand-foot-mouth disease, which has presented more in older kids for the past couple years than in previous years), but strep throat can't be entirely ruled out without examining your child. You can give ibuprofen or acetaminophen for pain and fever and see your doctor tomorrow.

Rash: This could be an infectious rash. Measles has become much more common but this could be a strep rash. I would see a physician ASAP