Does Mouthwash Reduce Risk of Oral STIs?

Although many people aren't aware of the risk, a number of sexually transmitted infections (STIs, formerly referred to as sexually transmitted diseases, STDs) can be spread through oral sex. gonorrhea, chlamydia, syphilis, HPV (human papillomavirus), and herpes can all be spread through fellatio (mouth-to-penis sex) and cunnilingus (mouth-to-female genitalia sex).

The most effective way to reduce the overall risk of oral STI transmission is screening, treatment, and using barrier methods for oral sex, including condoms and dental dams. However, recent studies have also begun to suggest that using antiseptic mouthwash, such as Listerine, may also be able to reduce the risk of some oral STI transmission. This article will explore how well mouthwash might help kill germs from STIs.

Close up of toothbrush and mouthwash
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It is theoretically possible to get HIV (human immunodeficiency virus) through oral sex. However, transmission through oral sex is thought to be quite rare. The risk of transmission of other STIs is much higher.

Can Mouthwash Help With Oral STIs?

There is a growing body of literature suggesting that mouthwash may play a role in reducing the risk of oral STDs. A 2017 study published in the journal Sexually Transmitted Infections looked at whether gargling with Listerine mouthwash could be an effective way to reduce the risk of oral transmission of gonorrhea.

What the study found was that after gargling for one minute, the men, who had all tested positive for live bacteria before the study, were half as likely to have living bacteria in their mouths afterward. (This was measured by bacteria on mouth swabs.)

This was a much greater reduction than for men who gargled with just saltwater. There was only a 16% reduction of living bacteria on mouth swabs in those men. Oral gonorrhea is a serious concern, in part because of the growing number of antibiotic-resistant cases. Antibiotics that typically would kill gonorrhea are becoming defenseless against it.

One study saw an increase in mouthwash use with age and a decrease in oral gonorrhea, but the correlation was not statistically significant, meaning what occurred in the study would likely not occur by chance. However, other studies, such as a 2018 review, did find mounting evidence on the potential effectiveness of mouthwash against gonorrhea in saliva.

Still, it's important to treat results with caution, and note that gonorrhea may be an exception among other STIs. An example of this is a 2005 study of people with herpes who used a 30-second rinse of Listerine, which also returned positive results.

They saw a significant reduction in active herpes virus for more than 30 minutes after mouthwash use. The effect had worn off by 60 minutes, but the researchers still saw a strong benefit in that time frame. In other words, the mouthwash helped right after people used it, but not necessarily long term.

Basic Research on Mouthwash and STIs

Unfortunately, there have not been too many studies looking at the effects of mouthwashes on STIs in the human body. However, several studies have examined the effects of such mouthwashes in vitro (in a test tube or culture dish). In such studies, both Listerine and chlorhexidine-based mouthwashes have been shown to limit the growth of both HIV and herpes viruses.

Those results can't be directly related to how the mouthwashes work in people, but it definitely makes research on the role of mouthwash in oral STD prevention something that scientists are likely to continue working on in the future.

It's worth mentioning that research has also examined the role of oral hygiene in limiting oral HPV infection. A large study published in 2013 in the journal Cancer Prevention and Research found that poor oral health was associated with oral HPV infection.

That study didn't look directly at the impact of mouthwash use on HPV infection. Researchers, however, did find an increased risk of HPV in people who used mouthwash for treating oral symptoms. However, that association was more likely to be about the fact that oral symptoms requiring mouthwash are associated with poor oral health.

Some people may just be wondering if Listerine is simply a magic bullet that kills all bacteria and viruses. The answer seems to be no.

The data on Listerine and STIs do not show that Listerine is equally effective against all pathogens. It does seem to do a good job of reducing the number of certain infections, but that effect isn't universal. Other pathogens, like rotavirus and adenovirus, are not as efficiently killed off by gargling.

A Word From Verywell

Right now, the best way to prevent the spread of oral STIs is to consistently use barriers for oral sex. However, that isn't always a practical option.

In that case, gargling with an antiseptic mouthwash such as Listerine before sex may reduce your risk of transmitting an STI to your partner. Theoretically, it's possible that gargling after sex might reduce your risk of catching such an STI as well. However, it's very hard to do that research ethically. As such, there aren't any clear data.

Is gargling with mouthwash as good as using oral sex barriers for preventing the spread of oral STIs? Absolutely not. However, it looks like, for at least some STIs, it is definitely better than doing nothing.

Sometimes STI prevention is about what's possible, not what's best.

There are many people who aren't willing to use barriers for oral sex but are happy enough to gargle. It may not be clear how much mouthwash helps, but it's certainly better than doing nothing at all.

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10 Sources
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