Role of smoking in inflammatory bowel disease: implications for therapy

The relationship between smoking and inflammatory bowel disease is now firm ly established but remains a source of confusion among both patients and do ctors. It is negatively associated with ulcerative colitis but positively a ssociated with Crohn's disease. In addition, it has opposite influences on the clinical course of the two conditions with benefit in ulcerative coliti s but a detrimental effect in Crohn's disease. These differences have been the subject of much interest and scrutiny with the hope that they may offer some insight into the pathogenesis of the two conditions and possibly lead to alternative therapeutic options. Nicotine is probably the principal act ive ingredient in smoking responsible for the association; trials have show n it to be of some benefit in ulcerative colitis, but further research is r equired to establish its therapeutic role, and the relevant mechanisms resp onsible for its action. In this article, we review the role of smoking in i nflammatory bowel disease and its implication for therapy.