Some of the more obvious signs of smoking involve the skin. The substances in tobacco smoke actually change the structure of your skin. Smoking causes skin discoloration, wrinkles, and premature aging. Your fingernails and the skin on your fingers may have yellow staining from holding cigarettes. Smokers usually develop yellow or brown stains on their teeth. Hair holds on to the smell of tobacco long after you put your cigarette out. It even clings to nonsmokers. - See more at: http://www.healthline.com/health/smoking/effects-on-body#sthash.W4nyBx6M.dpuf