From kissing alone you rarely get an STI. Saliva does not carry most STIs, so the chance of an STI from kissing is generally small. The exceptions are limited and easy to name: with gonorrhoea, kissing seems to play a role (Chow, 2019), and herpes or syphilis can pass on through a sore or cold sore in the mouth.
Kissing is part of intimacy, and most people do it without ever picking up an STI. Still, the question comes up often, especially after a deep kiss with someone new. This piece sets out honestly what does and does not travel through saliva, so you are not left guessing.
We are a testing provider, so let us say up front how it works: for most STIs there is no test that applies to kissing alone, and very often a test after kissing only is not needed either. Where a risk does sit somewhere, we name it per STI.
Can you get an STI from kissing?
Usually not. From ordinary kissing or deep kissing you seldom get an STI, because saliva does not pass on most of the causes in an infectious amount. The exceptions run through visible sores or blisters in the mouth, as with herpes or syphilis, and possibly through the throat with gonorrhoea. An STI from kissing is the exception, not the rule.
The difference is in how an STI is transmitted. Bacteria such as chlamydia need the lining of the genitals or throat and are not simply present in saliva. Viruses such as HIV do not survive in saliva in an amount that can infect someone.
Herpes and syphilis work differently: they can pass on through direct contact with an active wound or blister, and that can sometimes happen while kissing. That is exactly why the answer is not a simple yes or no, but depends on which STI you mean.
Which STIs can you get from kissing?
In short: herpes (HSV-1) through a cold sore, syphilis through a sore in or around the mouth, and possibly gonorrhoea through the throat. Chlamydia and HIV do not belong on this list, because they do not travel through saliva. Hepatitis B is theoretically conceivable, but only if blood or open wounds are involved.
The table below sets the main STIs side by side, with whether transmission through kissing is possible per STI and why. Look at the middle column: it separates the real exceptions from the myths.
| STI | Transmission through kissing? | Why (brief) |
|---|---|---|
| Gonorrhoea | Possible | Kissing was linked to throat gonorrhoea (Chow, 2019); evidence not settled |
| Chlamydia | No known route | Not passed on through saliva |
| Herpes (HSV-1) | Yes | Mainly with an active cold sore or blister on the lip |
| Syphilis | Yes | Through direct contact with a sore in or around the mouth |
| HIV | No | Saliva does not carry the virus in an infectious amount |
| Hepatitis B | Theoretically possible | Only with blood or wounds in the mouth, not through saliva alone |
What stands out: most rows say 'no' or 'no known route'. The uncertain cases turn on visible sores or on the throat, not on saliva itself. That makes panic after an ordinary kiss rarely necessary.
Can you get gonorrhoea from kissing?
Possibly, but the evidence is not settled. A large study of men in Melbourne found that kissing, even without sex, was linked to throat gonorrhoea (Chow, 2019). That points to an association, not a proven cause. Gonorrhoea can sit in the throat, and saliva or tongue-to-tongue contact could play a part in that.
Important to know: throat gonorrhoea often gives no symptoms at all. In a cohort of men who have sex with men, 92 percent of throat infections ran without symptoms (Morris, 2006). So someone can carry the bacterium in the throat without noticing it.
That makes gonorrhoea the only STI for which kissing is seriously studied as a route. Even so, unprotected oral or genital sex remains by far the main way throat gonorrhoea is picked up. Kissing is at most an additional, still unproven route.
Can you get herpes or syphilis from kissing?
Yes, these are the two STIs for which kissing is a real route. Herpes (HSV-1) mainly passes on with an active cold sore or blister on the lip. Syphilis can pass on through direct contact with a painless sore in or around the mouth. Without such a visible wound, the chance with both is much smaller.
Herpes type 1 is extremely common. According to the WHO, an estimated 3.8 billion people under 50, or 64 percent, carry herpes simplex virus type 1, which spreads mainly through mouth-to-mouth contact. A cold sore is therefore everyday and by no means always something to worry about. Through oral sex, HSV-1 can sometimes cause genital herpes.
Syphilis is rarer, but it starts with a painless sore (a chancre) that can also sit in the mouth. Contact with that sore, for example while kissing, can pass the bacterium on. More on herpes is in cold sore or genital herpes.
Can you get HIV or chlamydia from kissing?
No. HIV is not transmitted through saliva: there is too little virus in it to infect someone, so kissing, including deep kissing, does not count as a risk. Chlamydia does not travel through saliva either; that bacterium needs the lining of the genitals or throat and has no known route through kissing.
These are exactly the STIs people worry about unnecessarily after a kiss. For HIV, the virus does not occur in infectious amounts outside blood, semen, pre-ejaculate, breast milk and vaginal fluid. Saliva is not on that list, not even if small amounts of blood were present through, say, bleeding gums, which is not a known route of infection in practice.
Chlamydia can sit in the throat, but then it arrived there through oral sex, not through kissing. If you want to know what a throat infection with chlamydia or gonorrhoea actually does, read oral and throat STIs.
How big is the risk from kissing really?
For most STIs practically zero, and for the exceptions small to moderate. Ordinary kissing without visible wounds seldom passes on an STI. The risk only rises if an active cold sore or a sore is involved, or, with gonorrhoea, if the throat is already infected. Kissing is therefore usually low risk.
It helps to set kissing against what often happens around it. A deep kiss on its own is different from an evening that also involved unprotected oral or genital sex. It is almost always the latter where the real STI risk sits, not the kiss.
In the Netherlands, the RIVM tracks STI figures through the sexual health centres. According to the RIVM, gonorrhoea and syphilis remain stably high there, but transmission runs mainly through sex, not through kissing. Kissing is therefore rarely named as a separate risk factor.
When does an STI test make sense after kissing?
After kissing only, an STI test is usually not on the table, because the risk is small. Some people choose to have something checked if there was more than a kiss, for example unprotected oral sex, or if there is a persistent sore or blister in the mouth. What fits depends on the situation.
If there is a reason to look, it is almost never about kissing itself but about what else happened. For worries about the throat, an ordinary urine or blood test looks past the spot where an infection would sit; that needs a separate throat swab. Our test for chlamydia, gonorrhoea and trichomonas shows those infections with a PCR.
If you are unsure whether a vague throat complaint fits an STI, a sore throat from an STI takes you further. And because a throat STI often runs silently, a throat STI without symptoms explains why feeling nothing is no all-clear.
Two kisses, two different questions
Picture two evenings that both ended with a long deep kiss. On paper they look identical, but the question afterwards is completely different.
The first kiss was with someone with no visible cold sore, and nothing else happened. The chance of an STI from that kiss is close to zero, and worrying about it achieves little. Saliva simply carried no cause across.
On the second evening, the other person had a starting blister on the lip, and later there was also unprotected oral sex. Now two things are in play: herpes through the blister, and a possible throat infection through the oral sex. The same kiss as a starting point, but the kiss is not where the risk sat.
The difference was never in the kiss itself, but in what was visible and what else happened.
Further reading
This piece belongs to our cluster on STIs in the mouth and throat. For the wider overview, go to oral and throat STIs, where we set all the throat STIs side by side.
If your question is more about the complaints, read a sore throat from an STI or a throat STI without symptoms. If you are unsure about routes other than kissing, an STI from oral sex or a toilet seat covers the myths around that, and cold sore or genital herpes goes deeper into HSV-1.
References
- Chow EPF, et al. Kissing may be an important and neglected risk factor for oropharyngeal gonorrhoea: a cross-sectional study in men who have sex with men. Sexually Transmitted Infections, 2019. PMID 31073095.
- Morris SR, et al. Prevalence and incidence of pharyngeal gonorrhea in a longitudinal sample of men who have sex with men: the EXPLORE study. Clinical Infectious Diseases, 2006. PMID 17051493.
- World Health Organization (WHO), Herpes simplex virus, fact sheet. Accessed July 2026.
- RIVM, STI surveillance Netherlands. Accessed July 2026.
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