Our results revealed that nicotine significantly reduced the enhanced expression of IL-4 but not that of other Th2 cytokines in the spleen of OXZ mice and significantly suppressed the expression of every Th2 cytokine but not that of Th1 cytokine in the colon of OXZ mice, suggesting that the administration of nicotine ameliorates OXZ colitis mainly by suppressing the enhanced Th2 immune responses involved in mucosal immunity. Here, IL4 is linked to colitis.