How accurate is a syphilis and HIV test after 3 months? 9 months after unprotected sex I broke out into a rash (on the very last day of meds during a staph infection). They said it could be a reaction to the meds, but seemed unlikely to me since it was the very last day after having no reaction for a week. The rash covered my whole body, but went away after a day or 2 with antihistamines and other meds. Could this be a symptom of syphilis or other STD? Or something else I am not thinking of?