Absolutely. Many std's can be transmitted through oral sex including: herpes simplex, syphilis, hiv, gonorrhea, hpv & chlamydia. It is always best to know your std status & that of your partner(s). Getting tested at a clinic can help relieve anxiety about std's. Otherwise using a method of barrier protection (ie. Condom or dental dam) during oral sex will significantly reduce your chances of getting an std.
In addition to . The 6 std's that dr. Wainscoat listed, be aware that hepatitis may also be passed via oral sex. Hepatitis a can be transmitted via anal- oral sex (anilingus). If blood is co-mingled w other fluids – hepatits c can be transmitted via oral sex. Hepatitis b may be transmitted if infected fluids (semen, vaginal secretions, blood) come in contact w inflamed tissue/ sore/ulceration in throat or mouth.