[Tobacco and inflammatory bowel disease].

The relationship between tobacco and inflammatory bowel diseases is reported by many epidemiological studies. Smoking has a protective effect in ulcerative colitis. It delays the developing of the disease and improves the clinical pattern. Whereas smoking and passive smoking increase the risk of developing Crohn's disease. Tobacco is also a risk factor for severe symptoms, surgery and clinical relapses. The active substance was identified as nicotine. The major sites of nicotine effect are colonic mucus, intestinal permeability and cellular immunity. In practice, patients with Crohn's disease should stop smoking. Transdermal nicotine for ulcerative colitis could be effective.