Risks and causes of mouth and oropharyngeal cancer
We don’t know what causes most mouth or oropharyngeal cancers. But there are some risk factors that can increase your risk of developing it. These include smoking, drinking alcohol, and 
infection. Some people get mouth and oropharyngeal cancer despite not having these risk factors.
Mouth (oral cavity) cancer can start in different parts of the mouth, including the lips, gums, or soft sides. Oropharyngeal cancer starts in the oropharynx. This is the part of the throat (pharynx) just behind the mouth. It includes tonsil cancer and cancer in the back part of the tongue.
What is a risk factor?
Anything that can increase your risk of getting a disease is called a risk factor.
Different cancers have different risk factors. Having one or more of these risk factors doesn't mean you will definitely get that cancer.
Smoking
Smoking tobacco increases your risk of developing mouth and oropharyngeal cancer. This includes cigarettes, pipes and cigars. Research suggests that around 17 out of 100 (17%) of mouth cancers in the UK are caused by smoking.
People who smoke are more at risk if they also drink alcohol and chew betel quid with tobacco.
Exposure to environmental tobacco smoke for a long time causes a small increase in the risk of mouth and oropharyngeal cancer. This is also called passive smoking.
Alcohol
Drinking alcohol increases your risk of mouth and oropharyngeal cancer. It causes around 35 out of 100 (around 35%) of mouth cancers in the UK.
Smoking and drinking together further increase the risk of mouth and oropharyngeal cancer.
UK guidelines recommend a maximum of 14 units of alcohol a week for both men and women.
Chewing tobacco or betel quid
Smokeless tobacco is linked with causing mouth cancer. It includes:
- chewing tobacco
- betel quid (gutkha or paan) with or without tobacco
It is not a safe alternative to cigarettes.
Human papillomavirus (HPV)
The human papillomavirus (HPV) is a type of virus that infects the skin and the cells lining body cavities. Around 80 out of 100 people (around 80%) will be infected with HPV at some time during their lifetime.
For most people, HPV causes no harm and gets better on its own. You don't catch cancers like an infection. But the virus can cause changes in the mouth and throat. These changes are more likely to become cancerous in the future.
HPV spreads through close skin to skin contact, usually during sexual activity. The virus is very common. But only a very small number of people with HPV develop mouth or oropharyngeal cancer.
There are about 100 types of HPV and each one has a number. The main type of HPV found in mouth and oropharyngeal cancer is HPV 16.
The link to HPV is much stronger for oropharyngeal cancers than it is for mouth cancers. HPV causes around 50 out of every 100 (around 50%) of oropharyngeal cancers in the UK.
In recent years there has been an increase in HPV positive oropharyngeal cancer. Compared to HPV negative oropharyngeal cancer, people with HPV positive oropharyngeal cancers:
- are generally younger
- do not usually smoke
- drink little or no alcohol
People with HPV positive oropharyngeal cancer usually have a better outlook (prognosis). This is compared to those with HPV negative oropharyngeal cancers.
Age
Mouth and oropharyngeal cancer is a type of head and neck cancer. Most people getting head and neck cancers are aged 65 to 69 years.
Weak immune system
Your body's immune system fights infection. Some illnesses and medications can weaken your immune system. Research shows an increased risk of mouth and oropharyngeal cancer in people:
- with HIV/AIDS - there are higher rates of Human papillomavirus (HPV) infection in people with HIV
- taking medicines to suppress the immune system after an organ transplant
Mouth conditions
Changes can happen in the cells in the lining of the mouth. They can appear as red or white patches. The red patches are called erythroplakia, and the white patches leukoplakia.
In some people, these conditions may develop into cancer over some years. Doctors call these conditions precancerous.
Dentists can spot these patches during dental appointments. So, it is important to go for regular checkups.
Family history
Head and neck cancer risk is higher in people with a brother or sister (sibling) who had head and neck cancer. This is linked to having shared:
- lifestyle factors
- environmental factors
- genetic factors
Previous cancer
People who have the following cancers are also at increased risk of mouth cancer:
- a type of cervical cancer called squamous cell cancer
- cancer of the food pipe (oesophageal squamous cell cancer)
- lung cancer
Factors that might reduce the risk
Diet
Non starchy fruit and vegetables might reduce your risk of mouth and oropharyngeal cancer. Choosing a healthy diet might also reduce the risk of mouth and oropharyngeal cancer.
Physical activity
The risk of mouth cancer is lower in people who do moderate or high levels of physical activity. This is compared to those who do very little or no physical activity.
Other possible causes
There are often stories about potential causes in the media. It isn’t always clear which ideas are supported by evidence.
There might be things you have heard of that we haven’t included here. This is because either there is no evidence about them or it is less clear.
Reducing your risk
There are ways you can reduce your risk of cancer.
More information on risk factors for mouth or and oropharyngeal cancer
We have more detailed information for health professionals about mouth and oropharyngeal cancer risks and causes.
