 Recent study done by our laboratory shows that there are reduction in the number of E. coli in the gut of patients with arsenical keratosis which is increase by the administration of probiotics manuscript is preparing. However, E.coli contribute only about 0.1 of the total gut bacteria. It is not known whether anaerobic bacteria play an important role in the pathogenesis of arsenical keratosis. This can be evaluated by administering probiotics. Thirty patients of moderate arsenical palmer keratosis from an arsenic affected area will be recruited on the basis of inclusion and exclusion criteria. They will be provided two probiotics capsules per day orally for 12 weeks. Water sample will be collected before starting the study for confirming the diagnosis. Stool samples will be collected twice before and after completion of the study for qualitative and quantitative analysis of anaerobic bacteria. Similar number of arsenic exposed controls 30 and healthy volunteers 30 from the same area will be included in this study and they will be provided probiotics capsules with similar dosage and duration. Like aerobic bacteria, anaerobic bacteria may be modulated by probiotics in arsenicosis patients. 