Let me start off by saying that I am not in any way advocating for any specific relationship style – neither abstinence nor closed relationships would be a comfortable fit for me. There is certainly nothing wrong with open relationships or lots and lots of good sex.
With that out of the way, let’s get down to the nitty-gritty. Abstinence-only programs like to say that if you don’t have sex, you can’t get STD/STIs. They are wrong. You can get infected with both forms of herpes, HIV and Hep B without ever touching any genitals in any fashion. These infections are considered STD/STIs because they are often transmitted sexually, they are not only transmitted sexually. That said, it is true that the best protection available against STD/STIs really is to not have sex outside of sexually exclusive relationships. Really doesn’t matter how many people are in the relationship – whether you have 2 people or 10 people or even 200 people, if all of them join the relationship as virgins, and none of them ever have sex with anyone outside the relationship, then the chance of any of them getting and STD/STI are extremely low. The more people in the relationship, the higher the risk of something crazy happening, because statistics is like that. But it is fairly safe to say that is you have a sexually exclusive group of 5 or fewer people (none of whom are drug users), you chances of getting any STD/STI other than (possibly) herpes is damn near incalculable.
Herpes is the real joker in the deck. The blood born stuff (HIV and Hep) you are going to be safe from unless you play with needles (either S&M play or drug use) or just get insanely unlucky. Herpes, compared to most STD/STIs is insanely easy to spread. Partly, this is because herpes (both HSV1 and HSV2) can infect the mouth as well as the genitals. You can get either version of herpes by any form of skin contact with an infected area. Sometimes herpes (especially HSV1) can be spread by sharing sex toys, lipstick or drinks. This means that if your best friend goes down on someone with HSV2, they can get an oral infection of herpes, and the next time you and your friend share a soda, you can get infected. Now your closed poly quad is exposed to herpes, even though all of you were clean and none of you had sex outside the quad.
Aside from herpes, total abstinence outside of sexually exclusive relationships has a near perfect success rate. If STD/STIs are a real concern, and you can manage it, then establishing a closed relationship with people who have tested as clean of all STD/STIs can be the best way to protect yourselves.
STD/STIs and Cheating
The down side of abstinence or closed relationships as protection against STD/STIs is that staying abstinent or closed just doesn’t work for everyone. Most polyfolks are familiar with the high rate of cheating among monogamous couples. What you may not know is that cheating (defined by the individual) is actually pretty common in poly relationships. Now, here’s the kicker when it comes to STD/STIs. A recent study found that people who cheat are more likely to have sex without condoms, than people who are openly non-monogamous. Now, this study was comparing monogamous cheaters, but the results may apply to poly cheaters. If you can’t deal with a closed relationship, that’s okay. It’s better to have an open relationship and negotiate a safer sex agreement then risk your health and the health of your partners by going behind their backs.