How soon can STI appear on someone? Or does it depend on the person and the STI?
It depends on the STI and the person. For example, herpes takes about 3 weeks to show up after you have had contact with someone with herpes. For gonorrhea the incubation period is 2-10 days. A good rule to live by is not to wait for symptoms – especially because most STI and HIV do not have many symptoms! If you are sexually active then always practice safer sex (use condoms and dental dams) and go for STI and HIV testing every year.