Tobacco
Smoking or chewing tobacco is the greatest risk factor for developing oral cancer. The risk increases the longer a tobacco habit persists. About 90 percent of patients who are diagnosed with this type of cancer admit to using tobacco. About 37 percent of patients who continue smoking after they are treated will develop second cancers of the oral cavity, oropharynx or larynx, compared with only 6 percent of those who stop smoking. The risk of a second lung cancer in patients with head and neck cancer may be three times higher in men and nine times higher in women.
Pipe smoking carries a significant risk for cancers in the part of the lips that contact the pipe-stem. Smokeless tobacco ("snuff" or chewing tobacco) is associated with cancers of the cheek, gums and inner surface of the lips. Smokeless tobacco increases the risk of these cancers by about 50 times.
Alcohol
About 75 to 80 percent of all patients with oral cancer consume alcohol frequently, and oral and oropharyngeal cancers are about six times more common in drinkers than in nondrinkers. People who smoke and drink alcohol have a much higher risk of cancer than those using alcohol or tobacco alone. While scientists are not sure whether alcohol, like tobacco, damages DNA directly, they have shown that alcohol increases the ability of many DNA-damaging chemicals to penetrate cells.
Human papillomavirus (HPV)
HPV, especially in the presence of other risk factors may contribute to the development of some oral cavity and oropharyngeal cancers. Papillomaviruses are a group of about 80 related viruses that cause warts. Some types are associated with cancer can occur in up to half of oropharyngeal cancers. There is some evidence that tumors associated with HPV may have a better prognosis.
Ultraviolet light
More than 30 percent of patients with cancers of the lip have occupations associated with prolonged sunlight exposure. Many of these patients are fair-skinned with light hair and blue eyes.
Plummer-Vinson syndrome
This combination of iron deficiency with abnormalities of the tongue, fingernails, esophagus and red blood cells is associated with an increased risk of oral cancer. However, this syndrome is rare and is responsible for only a very small number of oral cancers.
Vitamin A deficiency
Vitamin A deficiency is associated with an increased risk of developing cancer of the oral cavity and oropharynx.
Mouthwash
Some studies have linked mouthwash with a high alcohol content with an increased risk of cancer in the mouth and pharynx. However, smokers and people who drink alcohol are more likely to use mouthwash than people who do not smoke or drink.
Immune-system suppression
People taking immunosuppressive drugs to treat immune-system diseases or to prevent rejection of transplanted organs may be at increased risk for cancers of the oral cavity and oropharynx.
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