The “main risk factor” is the number of partners someone has had oral sex with.

Oral sex is causing an “epidemic” of throat cancer, with the practice more damaging than smoking, drinking and poor diet.

It is now more common than cervical cancer in the UK and US, an expert has said.

Much of this is due to a particular type of throat cancer – oropharyngeal cancer – which affects the area of the tonsils and back of the throat and is caused by the human papillomavirus (HPV). HPV is also the leading cause of cervical cancer.

HPV is the name of a very common group of viruses, according to the NHS. It states that “they cause no problems in most people, but some types can cause genital warts or cancer. HPV affects the skin. There are over 100 different types.

Dr. Hisham Mehanna, from the UK’s University of Birmingham, said people with multiple oral sex partners were more than eight times more likely to develop the cancer.

Writing in The Conversation, Dr. Mehanna said: “Over the past two decades, there has been a rapid increase in oropharyngeal cancer in the West, to the extent that some have called it an epidemic.

Medical experts have identified HPV infection as the biggest risk factor for developing the disease.

“The prevailing theory is that most of us get HPV infections and are able to clear them completely,” Mehanna writes.

“However, a small number of people are unable to clear the infection, perhaps because of a defect in some aspect of their immune system. In these patients, the virus is able to replicate continuously and, over time, integrate into the host’s DNA at random sites, some of which can cause the host cells to become cancerous.”

Dr. Mehanna said that for oropharyngeal cancer, the “most important risk factor” is the number of partners someone has had oral sex with.

“Those with six or more lifetime oral sex partners are 8.5 times more likely to develop oropharyngeal cancer than those who do not practice oral sex,” he wrote.

According to Mehanna’s report, 80 % of adults report having engaged in oral sex at some point in their lives.

“But thankfully,” he asserts, “only a small number of these people will develop oropharyngeal cancer.”

According to the NHS, around 8,300 people are diagnosed with throat cancer each year, which is about 1 in every 50 cancers. More than 2 in 3 cases of throat cancer develop in adults over the age of 55. Only 1 in 8 (12.5 %) occur in people under the age of 50.