Smoking and IBD

Inflammatory bowel disease (IBD) is a term that primarily refers to two diseases of the intestines: Crohn’s disease and ulcerative colitis. These diseases cause chronic inflammation, and include symptoms such as severe abdominal pain, diarrhea, and rectal bleeding. In Crohn’s disease, the inflammation can be anywhere in the digestive tract, and can extend right through the entire thickness of the digestive tract wall, occurring in multiple patches or one large patch. In ulcerative colitis, the inflammation is limited to the inner mucosa of the bowel wall and begins at the anus, with the disease continuously progressing upward through the colon only.

We don’t know the cause of these diseases, but there is evidence suggesting that interactions among environmental factors, intestinal microorganisms, immune dysregulation, and genetic predisposition are likely responsible. We know that smoking is one of the environmental risk factors linked to IBD, and that it increases the risk of developing Crohn’s and can significantly worsen IBD symptoms.1 However, there are pronounced differences in how smoking affects people with Crohn’s compared to those who have colitis. Below is an overview of the impacts that smoking can have on people with IBD.


Crohn’s Disease and Smoking

Smoking is associated with a higher prevalence of Crohn’s and can increase the risk of developing it.1,2,3 These individuals who smoke also have a high risk of an increased disease severity, including increased relapse rates, a higher rate of corticosteroid, immunosuppressant, and biological drug use, narrowing of the gastrointestinal tract (stricture), increased rate of hospitalization and surgery, and more post-operative recurrence rates.4,5

A recently published study has also shown that peripheral arthritis is more common in people with Crohn’s who smoke or have a history of smoking (17.1% for ex-smokers, 16.9% for smokers, and 13.1% for non-smokers).5


Ulcerative Colitis and Smoking

In those with ulcerative colitis, smoking has different outcomes. Non-smokers are at a greater risk of developing it compared to current smokers.1,5 In addition, heavier smokers are less likely to develop ulcerative colitis than lighter smokers.3,6 Current smokers were less likely to have required long-term corticosteroid therapy than non-smokers.5 Researchers suspect that this phenomenon may be due to the release of a protective factor (the steroid-sparing effect of nicotine) in smokers with a genetic susceptibility to ulcerative colitis.3

Smokers were as likely to have undergone colectomy as people who never smoked and ex-smokers.5 Rates of hospitalization do not significantly differ for smokers and non-smokers.5 However, smoking correlates with an increase in ocular (eye or vision) problems.7



Smoking has detrimental effects on IBD-related symptoms and the long-term prognosis, especially in those with Crohn’s disease.

Even though non-smokers and ex-smokers with ulcerative colitis sometimes have more symptoms and require more treatment by corticosteroid treatments than heavy smokers require, there is no conclusive evidence of protective properties or substantial benefits of smoking in UC.5 The risks of smoking outweigh any potential health benefits.

We do not recommend that you smoke and hope you can urge friends and family to never start smoking. For advice on how to stop smoking, talk to your doctor or go to


Factors affected by smoking (and in some cases by nicotine)1

  • immune system
  • inflammatory cascade
  • gut mobility
  • mucus production
  • gut permeability
  • gut blood flow
  • platelet activation

First published in the Inside Tract® newsletter issue 196 – 2015
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1. Thomas G et al. Role of smoking in inflammatory bowel disease: implications for therapy. Postgraduate Medical Journal. 2000;76:273-279.
2. Nos P et al. Management of Crohn’s disease in smokers: Is an alternative approach necessary? World Journal of Gastroenterology. 2011;17(31):3567-3574.
3. Van der Heide F et al. Effects of active and passive smoking on disease course of Crohn’s disease and ulcerative colitis. Inflammatory Bowel Disease. 2009;15(8):1199-1207.
4. Cosnes J et al. Effects of cigarette smoking on the long-term course of Crohn’s disease. Gastroenterology. 1996;110(2):424-431.
5. Lunney P et al. Smoking prevalence and its influence on disease course and surgery in Crohn’s disease and ulcerative colitis. Alimentary Pharmacology and Therapeutics. 2015;42(1):61-70.
6. Aldhous MC et al. Smoking habit and load influence age at diagnosis and disease extent in ulcerative colitis. American Journal of Gastroenterology. 2007;102:589–597.
7. Roberts H et al. Extraintestinal manifestations of inflammatory bowel disease and the influence of smoking. Digestion. 2014;90(2):122-129.