Recently, a cancer sufferer was detained at an airport in the United States when immigration officials were unable to take a print from his fingers, his doctor reported in the medical journal, the Annals of Oncology. The patient, only referred to as Mr. S, was taking the drug capecitabine, which is sold under the brand name Xeloda and is used to treat several kinds of cancer. The drug carries side effects such as chronic inflammation of the palms or soles of the feet. Known as hand-foot syndrome, it can result in peeling of the skin, bleeding and development of ulcers or blisters. It also causes the very odd and very rare side effect of making your fingerprints completely disappear. Doctors say fingerprints usually return once the medication is stopped.