We don’t know what causes all mouth or oropharyngeal cancers. But there are some factors that can increase your risk of developing it. These include smoking, drinking alcohol, and HPV infection.
Mouth (oral cavity) cancer can start in different parts of the mouth, including the lips, gums or soft sides of the mouth. Oropharyngeal cancer starts in the oropharynx. The oropharynx 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 tobacco (cigarettes, pipes, cigars) increases your risk of developing mouth and oropharyngeal cancer. Research suggests that around 25 out of 100 of mouth and oropharyngeal cancers in the UK (around 25%) are caused by smoking.
People who smoke are more at risk if they also drink alcohol and chew tobacco or betel quid.
There is some evidence that people exposed to second hand smoke (passive smoking) for a long time have a small increase in their risk of mouth and oropharyngeal cancer.
Drinking alcohol increases your risk of mouth and oropharyngeal cancer. It causes around 35 out of 100 (around 35%) of mouth and oropharyngeal 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, including chewing tobacco, such as betel quid (gutkha) or paan is known to cause mouth cancer. It is not a safe alternative to cigarettes.
A diet low in fruit and vegetables may increase your risk of mouth and oropharyngeal cancer. This might be due to a lack of vitamins and minerals. A balanced diet usually means you are getting enough vitamins and minerals.
Human papilloma virus (HPV)
The human papilloma virus (HPV) is a type of virus that infects the skin and the cells lining body cavities. It is estimated that 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 over 100 types of HPV and each one has a number. The main type of HPV found in mouth and oropharyngeal cancer is HPV 16. HPV causes around 25 out of 100 mouth and oropharyngeal cancers (around 25%) in the UK.
The link to HPV is much stronger for oropharyngeal cancers than it is for mouth cancers.
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) compared to those with HPV negative oropharyngeal cancers.
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
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. White patches are called leukoplakia.
In some people, these conditions may develop into cancer over some years. Doctors call these conditions pre cancerous.
Dentists can spot these patches during your dental appointments, so it is important to go for regular check ups.
Research shows a slight increase in the risk of mouth and oropharyngeal cancer if you have a very close relative. For example, a parent or sibling who has head and neck cancer. Further research is needed to understand why this is.
People who have had a mouth or oropharyngeal cancer have an increased risk of getting a second cancer of the head and neck.
People who have the following cancers are also at increased risk of mouth and oropharyngeal cancer:
- a type of cancer of the cervix called squamous cell cancer
- cancer of the food pipe (oesophageal squamous cell cancer)
- lung cancer
Sunlight and sunbeds
Too much ultraviolet (UV) radiation from the sun or sunbeds is the main cause of skin cancer. Skin cancers are relatively common on the head and neck as these areas are more often exposed to UV radiation. Skin cancer can develop on the lip.
Research suggests that people who do little or no activity may have a bigger risk of developing mouth and oropharyngeal cancer. There are several research studies looking at reasons why physical activity might reduce the risk of cancer.
Blood pressure drug (hydrochlorothiazide)
Hydrochlorothiazide is a drug to treat high blood pressure (hypertension). A side effect is increased sensitivity to sunlight (photo sensitivity). A small study showed this medicine might lead to an increased risk of developing lip cancer.
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.