Are Rashes, A Side Effect Of Bactrim Intake In Children?

3 year old daughter diagnosed with UTI 6 days ago. Started on Bactrim (7.5 ml two times a day). This am woke with rash on ankle that has spread to other parts of body. It is not hives, but rash in nature. Does this mean she is allergic to Bactrim? Should she not take it in the future?