The risk of each infection in each kind of sex

Award winning clinic for healthcare and business quality standards in 2016 & 2018

This video is our medical director giving you a summary of the infections we see in oral, vaginal and anal sex. After watching, please select below the kind of sex that interests you to read more detailed information.



I would like to know more about the risks of oral sex



I would like to know more about the risks of vaginal sex



I would like to know more about the risks of anal sex



I’m in a relationship and have had sex with someone else – I’m very frightened!


I would like to do a complete sexual health check-up


I would like to know more about the risks of other sexual practices

Was the sex high risk? What are the risks in oral sex?


(1) Chlamydia, gonorrhoea, and syphilis


  • Oral Sex (mouth to penis)
  • Oral Sex (mouth to vagina or cunnilingus)

Receiving oral sex or giving it without a condom is the main way that gonorrhoea and chlamydia are transmitted according to what we see in Open House. One in every 17 men in whom we do a chlamydia test from the penis (urethra) is positive for chlamydia.
There are many cases with no symptoms, in the throat as well as in the urethra. If would like more information about the risk of catching gonorrhoea, chlamydia or syphilis in oral sex (mouth to penis) with someone who is infected, take a look at the table on the right.

Giving a woman oral sex is also a risk for gonorrhoea, chlamydia and syphilis, but is less common than mouth to penis.
Cases of syphilis have been described in women receiving cunnilingus, but it is not a very likely route of transmission for gonorrhoea and chlamydia.


(2) HIV and hepatitis B


  • Oral Sex (mouth to penis and cunnilingus)
  • Oral sex (mouth to anus)

Oral sex is not a major route of transmission for HIV and hepatitis B. The risk of HIV is practically zero, but there are some circumstances in which this risk rises slightly, albeit still being relatively low risk. Please see the diagram on the right.
The risk of hepatitis B is about 1% in all oral contacts (mouth to penis and cunilingus)

How can this risk be calculated unless people tell the truth?
It is extremely difficult to calculate the risk of HIV in oral sex because you have to identify people with the disease who have only ever practised unprotected oral sex, and often don’t want to admit the truth about other kinds of sex.
This situation is well illustrated if you read one study (that reports that in the UK only 13 cases of HIV were transmitted in oral sex from the 1980s up until 1998) with other studies published more than 15 years ago where a higher risk was reported, suggesting that oral sex is probably not a major route of transmission.

Beware of reading studies from the pre-medication era, because they conflict with the general consensus:
These studies also have tried to quantify risk. Some of them report a rate of between 3 and 16% of all positive cases being due to oral sex. But this is NOT our experience in Open House nor does it coincide with estimates made by health authorities. Also, these studies were performed in the pre-medication era, and this treatment dramatically reduces the infectivity of people with HIV.

  • Wound or abrasion on the genitals
  • Wound or abrasion in the mouth
  • Brushing teeth immediately before sex
  • Ejaculation (risk for the person who receives)
  • Co-transmission of gonorrhoea or chlamydia
  • The use of drugs during sex
  • Having syphilis

The risk of HIV in oral sex is zero in normal circumstances. If one of the following factors is present, then the absolute risk is low but not zero, and is around 0.01 to 0.05%.
We have done about 8000 HIV tests in people whose only contact was oral sex. Around 250 of these cases the sex was someone known to have HIV.
To date, we have only seen two possible cases in oral sex and they were due to co transmission of syphilis occurring at the same time.

Licking the anus is a risk for syphilis, hepatitis B and hepatitis A. The risk of each infection with someone infected for each disease is shown in the table on the bottom. If you need more information you can always write to us or book an appointment

Confused by what you’ve read? Three suggestions

How can we help you?



You can book a phone consultation with our doctors or come to Madrid to see them

Please trust our clinical judgement. Open House has done nearly 60.000 STI tests.

Caution! It is important to read about the Window Period before doing tests UNLESS YOU HAVE WORRYING SYMPTOMS

I would like to know more about the risks in vaginal sex


  • The Risks
  • Mycoplasma and ureaplasma:
  • Trichomonas

Vaginal sex is a more potent route of transmission of the viruses (hepatitis B and HIV) than oral sex, but both kinds of sex are potent routes for gonorrhoea, chlamydia and syphilis transmission.
Many of these infections exist without symptoms, especially if they are in a hidden part of the body (inside the vagina or in the cervix).
Take a look at this table which shows the risk of catching these diseases in vaginal sex with someone infected and the number of silent cases.
The risk of HIV is reduced if the sex was not prolonged, traumatic or if there was no ejaculation (less risk for the woman).
Being positive for one disease increases the risk of catching another.

These two bacteria’s are very infectious in vaginal sex and in fact, are only transmitted in this kind of sex (with a risk similar to that of gonorrhoea and chlamydia) but they are only considered a threat if they produce symptoms.

This parasite is an uncommon cause of vaginal infections or urethritis in men and is transmitted only in vaginal sex.


I would like to know more about the risks in anal sex


  • The Risks

Anal sex is the most potent route of transmission of all sexually transmitted disease, in heterosexuals and between men.
In our clinic, it is common to see patients who want to try to avoid pregnancy by practising anal sex, but they forget that it is the major way that HIV is transmitted.
As shown in the table on the right, if you have anal sex with someone infected with hepatitis B, the risk is about 100% chance of getting infected.
Similarly, (in the case of gonorrhoea, chlamydia or syphilis), the rectum can harbour these infections without any symptoms at all.

I would like to know more about the risks of other sexual practices


  • Sharing cocaine dosers
  • Fisting
  • Sharing dildos
  • Inoculation of bodily fluids into finger wounds
  • Group anal sex
Sharing cocaine dosers

At Open House 50% positive in a hepatitis C test had shared cocaine dosers, despite sexual contacts being a minor route of transmission. Its transmission occurs because of fragile blood vessels in the nose bleeding. However, cases of HIV transmission by this route have not been described

Fisting

Fisiting in groups (in parties) without gloves has been shown to be a powerful route of transmission of all sexually transmitted diseases. It is also a high risk activity for hepatitis C and lymphgranuloma venereum. They can be prevented using fresh gloves for each sexual partner when fisting.

Sharing dildos

The risks of gonorrhoea, chlamydia and syphilis are similar to those seen in anal sex.
Transmission of hepatitis C occurs in this kind of contact too.
Women sharing dildos have risk levels similar to those seen in vaginal sex.

Inoculation of bodily fluids into finger wounds

There is no data that supports whether HIV is transmitted in finger wounds or torn nail beds when in contact with precum, semen or vaginal fluids. It is believed that the wound must be bleeding to suppose a risk.

Group anal sex

Transmission of hepatitis C occurs in this kind of contact too. In fact, it may pass from the rectum of one person to the rectum of another by means of the penis that penetrated both people, even if a condom was being used.
In sex parties and dark rooms, the time between one penetration and another may be several minutes but hepatitis C can survive outside the body this period.

What would you like to do now?


I would like to know more about the risks of oral sex



I would like to know more about the risks of vaginal sex



I would like to know more about the risks of anal sex



I’m in a relationship and have had sex with someone else – I’m very frightened!


I would like to do a complete sexual health check-up


I would like to know more about the risks of other sexual practices

Where to find us

Calle Atocha 117, Madrid

Metro: L1 Atocha / Antón Martín

Contact Us

Call Us - 91 429 49 59

Cookie Policy | Privacy Policy | Legal Notice

The name Centro Médico Openhouse SLU, its logo and website content are protected by copyright. Our clinic and remote services are inspected and authorised by the Madrid Health Authority (registration number CS8003).

Centro Médico Openhouse SLU 2018 ®