In India, tobacco is used in both smoked and smokeless forms, but chiefly it is used in the smokeless form. Holding tobacco in the mouth allows the absorption of carcinogens present in it and also these orally absorbed carcinogens stays in the blood for a longer duration of time. Habit of chewing tobacco causes lesions in the oral cavity. These oral lesions can be precancerous or cancerous. If cancerous condition is known in the beginning of the disease, there are chances to recover from that. To fulfill that purpose we need some biomarkers that can predict the severity of the condition. One of the biomarker we used and checked for its reliability in the present study and that is known as Comet assay. Comet assay is a very versatile method, so can be used for any type of cells. The present study was undertaken to know the effects of chewing tobacco on blood cells of patients with precancerous and cancerous oral lesions. Comet assay was used as the biomarker for the assessment of the DNA damage. Results of the present study clearly show that the DNA damage was more in cancerous patients than the precancerous patients. The difference in DNA damage was highly significant (P<0.001) also. After the study we can say that comet assay is a reliable biomarker to assess the DNA damage. This study can be proven as a benchmark for future epidemiological studies in large populations

Tobacco, Oral lesions, Comet assay