Environmental factors in Crohn's disease

The most important environmental factor recognized in Crohn's disease is cigarette smoking. Smoking increases the risk of Crohn's disease and worsens considerably the course of the disease. Conversely, smoking cessation is followed rapidly by reversal of the effect. Persuading patients to stop smoking is probably the most cost-effective strategy for controlling disease activity. The contraceptive pill and appendectomy have no effect. The role of other environmental factors remains putative although dietary factors, which are the most difficult to study, may be important.