Suggest Treatment For Rashes On Hip,neck And Face

my son is 11 yrs old and recently had salmonella about 1 1/2 weeks ago. He has Iga deficiency so was treated with bactrim. He had a few round pink spots on his body while he was sick. He has been better for about a week and now he has developed a rash on his trunk, neck, and face. Should I be concerned?