Painless bisexual anal sex
Back to Sexual health. Having unprotected penetrative sex is the most likely way to pass on a sexually transmitted infection STI. Men who have sex with men MSM should have a check-up at least every 6 months at a sexual health or genitourinary medicine GUM clinic. This is important, as some STIs don't cause any symptoms. Find your local sexual health service. The infection is usually spread in contaminated food or drink, or by poor hand-washing.