Reverse smoking is an unusual form of smoking in which smokers place the lit end of the cigarette into the oral cavity and inhale the smoke. This particular form of smoking is prevalent on the Indian subcontinent. When the cigarette is held by the teeth and lips, the seal provided by the lips allows for a slower inhalation of the cigarette fume. In addition, moisture from the lip on the opposite end of the cigarette may allow for the cigarette to be consumed over a longer time period. Cigarette ashes are often swallowed in the process. The intraoral temperature can reach up to 120 degrees Celsius and the products of combustion increase the frequency of lesions inside the oral cavity when compared to conventional smoking. There is a relative paucity of epidemiological and controlled studies assessing these lesions.
In 2020, the World Health Organization (WHO) collaborating centre for oral cancer, defined palatal lesions in reverse smokers (PLRS) as ‘white and / or red patches affecting the hard palate in reverse smokers, frequently stained with nicotine’. These lesions were first described in the Indian state of Andhra Pradesh in the 1970s. Some of the changes in the palatal mucosa have a recognized malignant potential and PLRS are classified as an oral potentially malignant disorder (OPMDs).