Clinician collecting a throat swab

STIs from Oral Sex: Which You Can Catch and How to Test

Yes, you can get an STI from oral sex. Chlamydia, gonorrhoea, syphilis, herpes, hepatitis B and HIV can all be passed on this way, according to the NHS Open Doors service, although it is a less common route than vaginal or anal sex. The risk is real, it is easy to reduce, and a lot of these infections never cause a single symptom. So let’s be real about what actually happens, what to watch for and when testing makes sense.

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TL;DR

  • Oral sex can pass on gonorrhoea, herpes, syphilis, chlamydia, hepatitis B and HIV, and some, like gonorrhoea and herpes, are passed on more easily this way than others.
  • Giving oral sex carries a higher risk than receiving it, and cuts, sores or ulcers raise the risk for both of you.
  • Many STIs, including throat infections, have no symptoms, so a clear throat does not mean a clear result.
  • A condom or dental dam is the best protection, and the NHS suggests waiting up to 7 weeks after exposure to test if you have no symptoms.
  • Our at-home rapid kits give results in 15 minutes, with discreet packaging and free UK shipping.

Table of Contents

Which STIs can you catch from oral sex?

More than 30 bacteria, viruses and parasites can be passed on through sexual contact, and the World Health Organization includes oral sex in the ways they travel. In practice, the ones people most often ask about are these.

Gonorrhoea. One local NHS surgery lists gonorrhoea among the infections commonly caught through oral sex, alongside genital herpes, syphilis and HPV. It can settle in the throat. The NHS says gonorrhoea can affect the throat and cause a sore throat, and that you may be offered a throat swab if it does.

Herpes. The NHS explains that genital herpes is passed on through vaginal, anal and oral sex. You can also catch it from skin-to-skin contact when there are no visible sores, if a cold sore touches your genitals, or via fingers and shared sex toys. It is very easy to pass on from the first tingle or itch of a new outbreak until the sores have fully healed.

Syphilis. The NHS says syphilis sores can appear in the mouth or on the lips as well as on the genitals or anus. You can get it by touching an ulcer on a partner’s penis, vagina, bottom or inside their mouth, and unprotected oral sex counts.

Chlamydia. It is generally listed as less likely to be passed on through oral sex than gonorrhoea, but it can be, and throat chlamydia is a thing. More on that below.

HPV, hepatitis and HIV. The same local NHS surgery lists HPV as commonly caught this way, and puts hepatitis A, B and C, HIV, genital warts and pubic lice in the less frequently passed on group. Open Doors names hepatitis A and B and HIV as transmissible through unprotected oral sex too. The American Sexual Health Association says the chance of getting HIV from oral sex is very low, with few if any known cases.

STIs grouped by reported oral transmission frequency

So the short version: almost everything you can catch elsewhere can, in principle, be caught through the mouth. The odds just differ from one infection to the next.

Does the type of oral sex change the risk?

It does. Here is how it breaks down.

Situation What the health sources say
Giving vs receiving Risk is lower when you receive oral sex than when you give it (NHS inform)
Sores, cuts or ulcers Risk goes up if either partner has sores or cuts around the mouth, genitals or anus (NHS inform)
Mouth-to-penis The type of oral sex most likely to pass on STIs, per ASHA
Gonorrhoea and herpes More likely to be passed on by oral sex than other STIs, per ASHA

Why does giving carry more risk? NHS inform explains that viruses and bacteria can be found in semen, vaginal fluid or blood, and can travel more easily into a partner’s body through breaks in the skin. The lining of your mouth and throat is delicate, and tiny breaks are common.

That also explains a practical tip from Open Doors: avoid cleaning your teeth, flossing or using mouthwash just before or after oral sex, and skip crunchy foods like toast or crisps, because they can cause small cuts in your mouth that make it easier for infection to pass.

How easy is it to get chlamydia from oral sex?

This is the question people ask most, and the honest answer is: it is possible, but throat chlamydia behaves differently from the genital kind.

The 2026 UK national chlamydia guideline from BASHH (the British Association for Sexual Health and HIV) says throat infection is predominantly asymptomatic and not known to be associated with any significant morbidity. It also notes that up to 50% of people clear it on their own between testing and treatment.

That is useful context, but it does not make testing pointless. The bigger concern is that you can have a throat infection and genital infection at once, or pass it on without knowing. Gonorrhoea is a different story: BASHH’s 2025 guideline says throat gonorrhoea is mostly symptomless, though some people get a sore throat, and it recommends throat testing for everyone with genital gonorrhoea and their contacts.

If you want to read more about how the two infections overlap, our guide on having gonorrhoea and chlamydia at the same time covers it.

What are the symptoms of an STI from oral sex?

Often, nothing. The NHS is clear that many STIs have no symptoms, and that the only way to know for sure is to get tested. That is the thing that catches people out. You feel fine, so you assume you are fine.

When symptoms do show up, here is what to look out for:

  • A sore throat that will not shift, particularly with gonorrhoea
  • Sores or ulcers on the lips, in the mouth or around the genitals, which can point to syphilis or herpes
  • Tingling, itching or burning around the mouth or genitals before blisters appear, a typical herpes warning
  • Blisters, sores or warts around the genitals or anus
  • Unusual discharge, or pain when peeing
  • A rash, or unusual vaginal bleeding
  • Warts in the mouth or throat, although the NHS describes this as very rare

Symptoms alone cannot tell you which infection you have, or whether you have one at all. A sore throat after a cold is far more likely to be a cold. A sore throat after a new partner and no condom is worth a test.

One more thing on gonorrhoea: if the early signs sound familiar, our page on gonorrhoea symptoms in men and women lists them in more detail.

Are canker sores sexually transmitted?

No. The NHS says mouth ulcers, which many people call canker sores, are not contagious and should not be confused with cold sores. They are common and usually clear up on their own within a week or two.

Cold sores are the ones to think about. They appear on the lips or around the mouth, often starting with tingling, itching or burning. They are caused by the herpes virus, and as the NHS notes in its genital herpes advice, a cold sore touching the genitals can pass herpes on. If you have a cold sore, it is kinder to hold off on oral sex until it has fully healed.

How to lower your risk

You do not have to give up oral sex to look after yourself. A few habits do most of the work.

  1. Use a condom or a dam. Open Doors says this is the best way to protect against STIs during oral sex. A condom covers the penis. A dental dam or a cut-open condom covers the vulva or anus.
  2. Skip it during an outbreak. Sores, cuts, ulcers or cold sores raise the risk for both of you.
  3. Think about your mouth. Avoid brushing, flossing or mouthwash right before or after, and avoid sharp foods, to prevent tiny cuts.
  4. Do not share toys without cleaning or covering them. The NHS lists shared sex toys as a way herpes passes on.
  5. Talk before, not after. It is not romantic, but a quick “when did you last test?” beats weeks of worrying.
  6. Test between partners. Regular screening means any infection is found and treated before it spreads.

If you or a partner is treated for gonorrhoea, the NHS advises no vaginal, anal or oral sex until you have both finished treatment and tests show it has cleared.

When should you test after oral sex?

Timing matters, because testing too early can miss an infection that is already there.

The NHS says STIs can take up to 7 weeks after unprotected sex to show up on a test, and that if you have no symptoms it is best to wait 7 weeks. Different infections have different window periods, so our guide on when to test after unprotected sex is a handy next read.

The NHS also says to go to a sexual health clinic if:

  • you think you may have an STI
  • a sexual partner has symptoms
  • you are worried after sex without a condom or dental dam
  • you are pregnant and have symptoms
  • you are having sex with new partners

Here is a simple way to think about it:

  • You have symptoms now (sores, a persistent sore throat, discharge): do not wait. See a sexual health clinic or your GP, particularly if you have a sore throat, because a throat swab may be needed.
  • A partner tells you they have an STI: get checked promptly and avoid sex until you know where you stand.
  • No symptoms, but you are worried: note the date of the encounter and plan a test for around 7 weeks later. Test sooner if you want a first check, and repeat after the window.
  • New partners: test routinely, whether or not you use protection every time.

If the result is positive, do not panic. Most common STIs are treatable, and several can be cleared with a short course of antibiotics. Speak to a clinic or your GP to get the right treatment, and let recent partners know so they can test too.

Our take: testing should feel as easy as the decision to be careful

We built Rapidtest because we kept hearing the same thing: people know they should check in on their sexual health, but the queue, the appointment and the awkward conversation put them off. So they put it off. That is how infections fall through the cracks.

The point about oral sex is that it is often forgotten. People who always use condoms for vaginal or anal sex sometimes skip them for oral, and many assume a throat infection would announce itself. It usually does not. Regular screening is the simplest answer to a risk you cannot see.

That is why our kits are designed to give you results at home in 15 minutes, with full instructions and discreet packaging. Our range covers chlamydia, gonorrhoea, syphilis, HIV, hepatitis B and C, HSV-2 and HPV. Testing when it suits you, in private, is how we think proactive health care should work.

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FAQ

Can you get an STI from oral sex if nobody has symptoms?

Yes. The NHS says many STIs cause no symptoms, so a partner can pass an infection on without knowing they have it. Herpes can also be passed on through skin contact when there are no visible sores. Testing is the only way to know your status.

Is it easier to get an STI from giving or receiving oral sex?

NHS inform says the risk is lower when you receive oral sex than when you give it. Either way, cuts or sores around the mouth, genitals or anus raise the risk. A condom or dental dam lowers it whichever way round you are.

How long after oral sex should I wait to test?

The NHS says STIs can take up to 7 weeks to show up on a test, and suggests waiting 7 weeks if you have no symptoms. If you have symptoms, such as sores or a persistent sore throat, see a sexual health clinic straight away rather than waiting.

Can you get chlamydia in your throat?

Yes, though it is less common than gonorrhoea in the throat. BASHH says throat chlamydia is mostly symptomless and that up to half of people clear it before treatment. It is still worth testing, as you could pass it on, or have it elsewhere too.

Are canker sores a sign of an STI?

No. The NHS says mouth ulcers are not contagious. Cold sores are different, because they come from the herpes virus and can be passed on. If you are not sure which you have, ask your GP or a sexual health clinic.

Sources

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