ulcerative colitis,resulting in higher concentrations of the toxic gas hydrogen sulfide.the role hydrogen sulfide in pathogenesis is unclear.if has been suggested that the protective benefit of smoking that some patients report is due to hydrogen cyanide from cigarette smoke reacting with hydrogen sulfide to produce the nontoxic isothiocyanate.another unrelated study suggested sulphur contained in red meats and alcohol may lead to an increased risk of relapse for patients in remission.