Some types of oral cancer are linked to human papilloma virus (HPV) infection in the mouth and throat. Find out the possible risks of this infection from oral sex, and how to protect yourself.
Oral cancers are sometimes called head and neck cancers, and include cancers of the mouth, lip and tongue, as well as cancers of the tonsils, oesophagus, larynx (voice box), nasopharynx (the area that connects the nose and throat) and the thyroid gland.
What causes oral cancer?
Experts have known for years that the main risk factors for oral cancer are drinking alcohol and smoking or chewing tobacco. But there is growing evidence that infection in the mouth with HPV is a major cause of oral cancer.
Around 25% of mouth and 35% of throat cancers are HPV-related, but the exact figures vary between different studies, possibly due to different ways of testing for the virus, or varying levels of smoking and other risk factors.
Detecting the HPV virus in a sample of people who have oral cancer does not mean that HPV caused the cancer. The virus becomes part of the genetic material of the cancer cells, triggering them to grow.
How do you get HPV in the mouth?
There are more than 100 types of HPV, and around 15 are associated with cancers. These 15 are known as high-risk HPV types.
The types of HPV found in the mouth are almost entirely sexually transmitted, so it's likely that oral sex is the primary route of getting them. The high-risk HPV types are also passed on through vaginal and anal sex, and are linked to:
Some can be passed on through skin-to-skin contact and cause warts, including genital warts . The types of HPV that cause visible warts are low-risk and are not the same types that cause cancer.
Most sexually active people (about 90%) will have been exposed to either high- or low-risk genital HPV types by the age of 25, but only 2-3% of these people develop visible genital warts. So most of us have been infected, but few are affected.
It's not known how common HPV infection in the mouth is. A study carried out in 2009-10 concluded that the prevalence of oral HPV infection in American men was 10%, and in women 3.6%. Risk factors for oral HPV identified by this study included:
- age : prevalence peaked in the 30-34 and 60-64 age groups
- number of sexual partners : 20% of people with more than 20 partners had an oral HPV infection
- current number of cigarettes smoked per day
There is good evidence suggesting that, for some oral cancers, risk factors may be linked to sexual behaviour. These risk factors include:
- ever having oral sex
- having oral sex with four or more people in your lifetime
- among men, first having sex at an earlier age (under 18)
Currently, there is very little research that has looked at the possible risks from giving oral sex to a man compared to giving oral sex to a woman. But we do know that HPV-related oropharyngeal cancer is twice as common in men than women, and is most common in heterosexual men in their 40s and 50s (compared to the rates in homosexual men).
This indicates that performing cunnilingus (oral sex on a woman) is more risky that performing fellatio (oral sex on a man). This seems counterintuitive, but the concentration of HPV in the thinner, moist skin of the vulva is much higher than the amounts of virus shed from the thicker, dry skin of the penis, and this affects how easy it is to pass the virus on. Other research indicates that HPV can be present in semen and passed on at ejaculation.
What is definitely known is that other infections are spread via oral sex, including herpes , chlamydia, syphilis and gonorrhoea , so it makes sense to protect yourself and your sexual partner by practising safer oral sex.
How does HPV cause cancer?
HPV does not directly give you cancer, but it causes changes in the cells it has infected (for example, in the throat or cervix), and these cells can then become cancerous.
Very few people infected with HPV will develop cancer. In 90% of cases, the infection is cleared naturally by the body within two years.
However, people who smoke are much less likely to clear the virus from their body. This is because smoking damages special protective cells in the skin called immune surveillance cells, allowing the virus to persist. Cervical and vulval cancer is rare in women who don't smoke, unless they have some other cause of immunosuppression (a weakened immune system).
If cell changes do happen, it can take a long time – even decades. HPV-related oral cancers seem to respond better to treatment than non-HPV-related oral cancers.
Could an HPV vaccine help men as well as women?
Yes. In the UK, girls aged 12 and 13 are routinely given the HPV vaccine . This is because it is known that nearly all cervical cancers are HPV-related and that the vaccine offers protection in women. The vaccine also protects women from HPV-related vulval and vaginal cancers.
In addition, it will probably protect them from anal and oral cancer. There is currently no conclusive proof that the vaccine will protect against oral cancer, but it's thought likely, because HPV causes mouth, throat and anal cancer in the same way that it causes cervical cancer.
In time, as the HPV vaccine reduces the number of cases of HPV infection in women, HPV will become less common in the general population – therefore, it will affect fewer men as well as fewer women. This has already happend in Australia, where cases of genital warts have fallen dramatically in women and heterosexual men under 21 within four years of the start of the vaccination campaign.
However, a vaccination given only to girls and women will not benefit men who have sex with men.
Boys and men are not routinely given the HPV vaccine in the UK. This is because they do not need to be protected against cervical cancer. Emerging evidence on the impact of HPV vaccination on other cancers is being reviewed by the Joint Committee on Vaccination and Immunisation.
Men who have sex with men may have an increased risk of anal cancer, linked to HPV infection, and made worse by co-infection with HIV. There is evidence that the HPV vaccination may protect against HPV-related anal cancer, and recurrence of anal pre-cancer after treatment.
If you are worried
If you're worried about oral cancer, see your doctor. When mouth cancer is established, it has fairly clear symptoms, and your doctor should be able to see them by looking in your mouth. If oral cancer is diagnosed early, it is easier to treat, but about half of these cancers are diagnosed when the disease has already spread within the neck.
The symptoms of oral cancer include:
- red – or red and white – patches on your tongue or the lining of your mouth
- one or more mouth ulcers that do not heal after three weeks
- a swelling in your mouth that lasts for more than three weeks
- pain when swallowing
- a feeling as though something is stuck in your throat
Read about the symptoms of oral cancer .
Safer oral sex
You can make oral sex safer by using a condom on a man’s penis, because it acts as a barrier between the mouth and the penis. A dam (a square of very thin, soft plastic) across a woman’s genitals can protect against infection.
Find out more about STIs and safer sex.