Some types of cancer are linked to human papillomavirus (HPV) infection in the mouth and throat. It's likely that some types of HPV are spread by oral sex. Cancers in the mouth and throat are sometimes called head and neck cancers, and include cancers of the: mouth

lip

tongue

voice box (larynx)

area that connects the nose and throat (nasopharynx)

What causes cancer in the mouth and throat? The main risk factors for mouth and throat cancer are drinking alcohol and smoking or chewing tobacco. But there's growing evidence that an increasing proportion of cancer is caused by HPV infection in the mouth. Around 1 in 4 mouth cancers and 1 in 3 throat cancers are HPV-related, but in younger patients most throat cancers are now HPV-related. Detecting the HPV virus in a sample of people who have oral cancer does not mean that HPV caused the cancer.

How do you get HPV in the mouth? 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. There are more than 100 types of HPV and around 15 are associated with cancers. These 15 are known as high-risk HPV types. They're also passed on through vaginal and anal sex, and are linked to cancer of the cervix, anus and penis. 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.

How common is HPV in the mouth? We do not know for sure. A study carried out in 2009-10 concluded that 1 in 10 American men and less than 4 in 100 American women had HPV infection in the mouth. Another study published in 2017 found that in America, 6 in 100 men and 1 in 100 women carried potentially cancer-causing types of HPV in their mouth. This was more common in smokers and in men with more oral sex partners. The study did not link a specific number of partners with the risk of carrying HPV in the mouth, or of cancer. This study also looked at how common mouth and throat cancers were in people carrying these harmful types of HPV, and found it's still very rare: around 7 in 1,000 men and 2 in 1,000 women.

Is it more risky giving oral sex to a woman or a man? There's very little research that's looked at the possible risks from giving oral sex to a man compared with giving oral sex to a woman. But we do know that HPV-related oropharyngeal cancer (the part of the throat directly behind the mouth) is twice as common in men than women, and is most common in heterosexual men in their 40s and 50s. This may indicate that giving oral sex to a woman is more risky than giving oral sex to a man. The concentration of HPV in the thinner, moist skin of a woman's genitals (the vulva) is much higher than the amounts in the thicker, dry skin of the penis. This could affect how easy it is to pass the virus on. Other research indicates that HPV can be present in semen and passed on at ejaculation. But there are other differences in sexual behaviour between men and women that may also explain the differences in the rate of cancer, including the number of sexual partners.

How does HPV cause cancer? HPV does not directly give you cancer, but it causes changes in the cells it's infected (for example, in the throat or cervix) and these cells can then become cancerous. If cell changes do happen, it can take a long time, even decades. Very few people infected with HPV will develop cancer. In 9 out of 10 cases, the infection is cleared naturally by the body within 2 years. But 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, allowing the virus to persist.

If you're worried If you're worried about cancer of the mouth or throat, see your GP. When mouth cancer is established, it has fairly clear symptoms and your GP should be able to see them by looking in your mouth. Cancer is easier to treat if it's diagnosed early, but about half of these cancers are diagnosed when the disease has already spread within the neck. The symptoms of mouth and throat cancer include: red, or red and white, patches on your tongue or the lining of your mouth

1 or more mouth ulcers that do not heal after 3 weeks

a swelling in your mouth that lasts for more than 3 weeks

pain when swallowing

a feeling as though something's stuck in your throat