An inverse association between cigarette smoking and ulcerative colitis
has been repeatedly documented. The relationship is complex, since
current smokers have a markedly reduced risk relative to never smokers
(as low as 0.4 or lower), but former smokers have, if anything, an
increased risk.
Reports of the amelioration of ulcerative colitis symptoms by
smoking or nicotine administration led to formal trials of transdermal nicotine. The pattern of response resembles that of corticosteroid
therapy: transdermal nicotine aided the treatment of patients in
relapse but a somewhat less intense nicotine regimen was ineffective in
prolonging remission Thus there is considerable evidence that smoking—and nicotine in
particular-has a beneficial effect in ulcerative colitis. The effect remains
unexplained, although several mechanisms have been proposed, including
changes in bowel mucus or prostaglandins, immune suppression, and
other effects in the bowel89
.