The exact causes of the different types of head and neck cancer are unclear. The cancer appears to be the result of damage to the DNA of the cells in the head and neck region, which causes them to become malignant and rapidly reproduce as cancer cells.

However, a number of risk factors are linked to the growth of cancerous cells. Tobacco use has the strongest link to head and neck cancer. In addition to cigarettes, tobacco use includes cigar and pipe smoking and smokeless tobacco (e.g., chewing tobacco, snuff).

Research has shown that tobacco causes damage to cells in the lining of the mouth, pharynx and larynx. Cells must grow more rapidly to repair this damage. Many of the chemicals found in tobacco cause damage to DNA, which tells the cells how to grow and repair the damage. In essence, tobacco both damages cells and inhibits the ability to grow new ones.

The National Institutes of Health (NIH) estimates that approximately 85 percent of head and neck cancers are linked to some form of tobacco use. Smokers are 6 times more likely to develop oral or upper throat cancers than nonsmokers. The risk of developing head and neck cancers increases with the amount of tobacco smoked, chewed or sucked and the duration of use.

Secondhand smoke, also known as environmental tobacco smoke (ETS), may contribute to the development of head and neck cancers. When nonsmokers are exposed to secondhand smoke, they can absorb nicotine and other chemicals similar to the way smokers do. The greater the exposure to secondhand smoker, the greater the level of compounds in the body.  There are no specific statistics as to the risk of head and neck cancer due to secondhand smoke exposure.

Alcohol use has the second strongest link to head and neck cancers. Drinking alcohol significantly increases the chances of developing oral, oropharyngeal and laryngeal cancers. The American Cancer Society (ACS) estimates that 75 to 80 percent of all patients with oral cancer drink excessive amounts of alcohol. Head and neck cancers are about 6 times more common in drinkers than nondrinkers.

Scientists are unsure if alcohol directly damages the DNA, but they have shown that alcohol increases the penetration of many DNA-damaging chemicals into the cells. This is one reason why tobacco and alcohol use together cause such a large amount of DNA damage.

The risk factors for head and neck cancer change according to the amount, types, and length of use for both alcohol and tobacco use. In addition, the combination of smoking and drinking also increases the risk.

Other risk factors are also associated with developing head and neck cancers. These include:

• Age. The likelihood of developing head and neck cancer increases with age. Approximately 50 percent of all the cases are over the age of 65.
  
  
• Gender. Head and neck cancers are twice as common in men as women. The highest occurrence is in men over age 50. This statistic may be related to the higher incidence of alcohol and tobacco use by men.

• Sunlight. Prolonged exposure to sunlight can damage the cells on the lips. The ACS estimates that more than 30 percent of people with cancer of the lip have occupations associated with outdoor exposure.
  
  
• Mouth irritation. Poorly fitting dentures that cause long-term irritation of the mouth’s lining is thought to be a risk factor for oral cancer. Poorly fitting dentures may allow causative cancer agents, such as alcohol and tobacco particles, to be trapped under them. However, many research studies have not shown any difference in the occurrence of oral cancer between denture wearers and non-denture wearers.
  
  
• Poor nutrition. A diet that is low in fruits and vegetables is associated with an increased risk of developing cancer in the oral cavity and oropharynx. Without fruits and vegetables, the cells are deprived of the nutrients that help keep them healthy and antioxidants that are protective.
  
  
• Human papillomavirus (HPV) infection. Papillomaviruses are a large group of related viruses (e.g., herpes), some of which have a role in causing cancer. HPV is one of the most common causes of sexually transmitted diseases. One type of HPV (HPV-16) is thought to be linked to oral and oropharyngeal cancers. The links have been inconclusive at times, but a recent study made a strong link between HPV-16 infection and oropharyngeal cancer.
  
  
• Immune system suppression. For reasons that are not clear, individuals who are taking immunosuppressive drugs are more at risk for oral and oropharyngeal cancers. These drugs are taken to treat immune system diseases or to prevent the rejection of a transplanted organ.
  
  
• Industrial exposures. Inhalation of certain industrial elements, such as wood and nickel dust, may contribute to the development of head and neck cancers. It is most strongly linked to cancer of the sinuses, nasal cavity and pharynx. Exposure to airborne particles of asbestos is linked to cancer of the larynx.
  
  
• Radiation. Radiation to the head and neck can increase the risk of head and neck cancer, particularly for the salivary glands. The radiation exposure can come from diagnostic x-rays or radiation therapy for medical conditions, such as an earlier case of cancer.
  
  
• Epstein-Barr virus. This common virus is present in most of the cancer cells associated with nasopharyngeal cancer, an uncommon cancer in the United States. The relationship between the virus and the cancer is unclear. The virus is extremely common, but the cancer is not. 

Although there are no hereditary factors clearly identified with most forms of head and neck cancers, a recent study has identified genetic alterations in the tissues around certain head and neck tumors. These tissues were associated with the aggressiveness of the tumors.