Let's Talk About Sex #2: Can Alcohol Kill Bacteria?

So today's blog is going to explore another question from one of my male college students - "Can drinking alcohol after oral kill any bacteria in my mouth?" Wouldn't it be great if you could simply chug a beer or throw back a shot of tequila after giving oral to kill any bacteria? We know that you can become infected with an STI during oral sex in a couple of ways - by giving oral sex to a partner infected with an STI (e.g., you go down on a partner who has a chlamydia infection), by receiving oral sex from a partner who is infected with an STI in their throat (e.g., a partner with a chlamydia infection in their throat goes down on you), or by orally stimulating the anus of a partner who is infected with a rectal STI (e.g., you give analingus, or a "rim job," to a partner with rectal gonorrhea). Since studies have found that more than 85% of sexually active adults (ages 18-44-years old) have engaged in oral sex, we need to be real about the risks and how to practice safe sex.

When I first read this question, I was pretty sure that there was no way drinking alcohol would kill any bacteria in your mouth and throat. But then I started to wonder. Didn't people use alcohol to clean wounds and reduce infections way back when? Why wouldn't it be possible to reap the same effects from drinking alcohol after oral? I remember hearing stories about how Listerine mouthwash was used to treat gonorrhea infections back in the early 1900s. Then I found a fairly recent study published in the journal of Sexually Transmitted Infections that reported men who were culture positive for oral gonorrhea (had already tested positive) and gargled Listerine for one minute significantly reduced gonorrhea bacteria in their mouths (for more information about this study, go to http://sti.bmj.com/content/early/2016/11/29/sextrans-2016-052753).

Scientists believed that it was probably the 21% alcohol in the mouthwash that decreased the bacteria. While beer has a lower alcohol content (around 4-6%), a shot of tequila has a higher alcohol content (around 31-55%). So it seems to make some sense that doing a shot could potentially kill some bacteria. But it's not clear. In the study I just cited, the men were already infected with gonorrhea in their throats and reducing the amount of the bacteria didn't eliminate the STI, it just reduced the amount of the infectious agent. Since we know that it doesn't take much of the gonorrhea bacteria to cause an infection, this cannot be viewed as an effective method for minimizing STI risk. At the end of the day, the most effective method for avoiding STIs during oral sex is to use a condom or a dental dam (or be in a monogamous relationship in which both of you have been tested).