Binge drinking and smoking may be fuelling an increase in mouth cancer among young people, say experts.
More than 4,000 cases of oral cancer are diagnosed each year
The British Dental Health Foundation is warning people of all ages to check their mouth regularly.
Previously, it was thought that older people were particularly vulnerable to the disease.
Men are still twice as likely to develop the disease - but it has also become increasingly common in women in the last 10 years.
Mouth cancer, which can affect the lips, tongue, cheeks and throat, kills 1,700 people in the UK every year. Some 4,300 new cases are diagnosed every year.
The condition is also linked to a poor diet.
But people who smoke and drink a lot of alcohol are up to 30 times more likely to develop the disease than those who do neither.
Dr Nigel Carter, chief executive of the BDHF, said: "In the UK, mouth cancer kills one person every five hours and it is no longer just older males who need to be worried about developing mouth cancer - the condition can strike anyone.
"Regular self-examination is now the norm for breast cancer and testicular cancer, and it needs to be the same for mouth cancer.
"Of course you can cut your risk considerably by leading a healthy lifestyle, so giving up smoking, cutting down on alcohol and eating a healthy diet is still very important.
"However, with one in four younger sufferers living healthily prior to developing the condition, the importance of self-examination cannot be underestimated."
The first sign of mouth cancer is often a non-healing mouth ulcer or a red or white patch in the mouth.
The BDHF said that people should visit the dentist as a precaution if they notice any changes in their mouth as early detection significantly increased the chances of survival.
Dr Lesley Walker, of Cancer Research UK, said a large majority of cases of mouth cancer still occurred in people over 50.
"Nevertheless, it is important to see your doctor or dentist if you notice any persistent changes in your mouth, such as ulcers, lumps or red or white patches.
"Mouth cancer can be treated successfully in most cases, if diagnosed early."