 The role of anaerobic bacteria in the pathogenesis of palmer arsenical keratosis is not known. This can be evaluated by administering probiotics. Thirty patients from an arsenic affected area will be provided two probiotics capsules per day orally for 12 weeks and stool samples will be collected for qualitative and quantitative analysis of anaerobic bacteria. Similar number of arsenic exposed controls and healthy volunteers from the same area will be included with similar protocol for comparison. Like aerobic bacteria, anaerobic bacteria may be modulated by probiotics in arsenicosis patients. 