Smokeless tobacco and head and neck cancer: there is risk even without fire.

The use of smokeless tobacco (primarily moist chewing tobacco) is currently on the rise in the USA. Smokeless tobacco contains many carcinogens. Multiple large-scale epidemiologic studies have been completed to evaluate the risk of cancer associated with use of smokeless tobacco. This article will review the current knowledge of the mechanisms of carcinogenesis and the relative risk these products impart to the users.