Which stds can cause rectal bleeding?

Several STDs...: Several sexually transmitted infections can involve the anus, rectum, and colon, including syphilis, chancroid, herpes, gonorrhea, chlamydia, to name a few. If you believe you may have a sexually transmitted infection, you should see a doctor to be tested, because they all have different treatments. Regardless, any unexplained rectal bleeding should be medically evaluated.