Smokeless tobacco keratosis (STK) is a condition of the oral mucosa resulting from the chronic use of smokeless tobacco products. Mechanical friction against the oral mucosa, combined with chemical exposure to nicotine and nitrosamines, induces keratinization. Early lesions present as a thin, white-to-gray filmy patch that thickens with continued irritation, developing a wrinkled appearance. The location of the lesion typically corresponds to where the smokeless tobacco product is held, commonly the upper or lower labial vestibule or buccal area, and less frequently the palate or floor of the mouth. Lesions usually develop within a few years of regular smokeless tobacco use.