Last reviewed: November 2017

If you have Crohn’s or Colitis and are a smoker, you may wonder whether this has an effect on your disease.

The relationship between smoking and Crohn's and Colitis is complex. Many studies have shown that people who smoke are more likely to develop Crohn’s Disease, and research suggests that smoking increases the severity of the disease. In contrast, smoking appears to decrease the severity of Ulcerative Colitis, although it still carries many other health risks.

This information is for people living with Crohn's and Colitis who smoke. It looks at the evidence for the different effects of smoking on these two conditions, and what it may mean for people with Crohn's or Colitis. It also looks at ways to help you give up smoking.

Download this information (PDF).

  • Smoking and Crohn's Disease

    How does smoking affect Crohn’s?

    Smoking increases the risk of developing Crohn’s Disease. Research also suggests that smoking can make Crohn’s worse.

    People with Crohn’s who smoke may find that they:

    • Have more severe symptoms and complications such as strictures, or narrowings in the bowel that can cause dangerous blockages
    • Are more likely to develop fistulas, abnormal passageways in the body that often require surgery
    • Have more flare-ups
    • Require more immunosuppressant drugs, such as steroids, and biologic drugs – and sometimes these drugs are not as effective in people who smoke
    • Are more likely to need surgery and to have to return for further surgery
    • Are more likely to develop extraintestinal manifestations – additional complications in other parts of the body – such as osteoporosis (weak bones), arthritis, skin disorders and eye disorders

    Research suggests that women who smoke are more likely to develop Crohn’s Disease, and to require surgery, than men who smoke.

    How does smoking make you susceptible to Crohn’s?

    We do not know, although there are lots of theories. Tobacco smoke contains more than 1,000 chemicals including nicotine, carbon monoxide and free radicals. There are a number of ways in which these chemicals may affect the gut. Smoking can change the bacteria that live in the gut, influence how a person’s genes function and cause changes to the immune system – all of which may make a person more likely to develop Crohn’s.

    What about the risk of passive smoking?

    Studies into the effect of passive smoking on Crohn’s Disease are inconclusive. Some studies suggest babies and children exposed to cigarette smoke may be more likely to develop Crohn’s. Another study suggests that adults with Crohn’s who are exposed to passive cigarette smoke may need more drug treatments, but more research is needed to determine whether these relationships are true.

    The lack of understanding between passive smoking and Crohn’s may in part be due to difficulties in measuring how much smoke someone is exposed to through passive smoking.

    Smoking during pregnancy is not advised for anyone, whether or not they have Crohn’s, due to the risks to the unborn baby.

    If I am a smoker now, is it worth giving up?

    Researchers and health professionals agree that giving up smoking is beneficial for people with Crohn’s Disease. UK and European guidelines strongly recommend that people with Crohn’s do not smoke.

    In the non-smoker, Crohn’s appears milder. Once you have stopped smoking for one year, the chances of a flare-up may be as low as for someone with Crohn’s who has never smoked. People who continue to smoke are more than twice as likely to have a flare-up compared to people who have stopped smoking.

    Smokers are also more than twice as likely to need surgery, to experience a recurrence of disease after surgery and to need a second surgery. However, stopping smoking can reduce these risks to the rates of people who have never smoked.

    Even reducing the amount you smoke may have a positive effect on your symptoms. Studies have shown that heavy smokers develop more extraintestinal manifestations (additional complications in other parts of the body), have more strictures, and are more likely to need to have part of their intestine removed than people who do not smoke as much. This suggests that, although completely stopping smoking has the best outcome, reducing the amount you smoke can also help. However, even light smokers with Crohn’s have more active disease on average, a greater hospitalisation rate and a higher likelihood of needing surgery.

    Considering all available evidence, it is widely advised that people with Crohn’s disease stop smoking. See the section on Can I get help to give up smoking? for further information.

    I have Crohn’s Disease and I smoke. I have tried to give it up but I find it really hard as it is part of my daily routine. My consultant always advises me of the detrimental effect it can have on my condition, which does make me think a bit more about giving up. 

    Diagnosed with Crohn's Disease in 1995

  • Smoking and Ulcerative Colitis

    How does smoking affect Ulcerative Colitis?

    Research shows that Ulcerative Colitis is less common in smokers than non-smokers. Some people have developed Colitis once they have given up smoking.

    While most studies show that smoking may delay or prevent a person from developing Colitis, it is still unclear whether smoking affects the progression or course the disease takes. Some studies show that smokers with Colitis suffer a milder form of the condition. Flare-ups, hospitalisation rates, the need for oral steroids or immunosuppressants, and colectomy rates have all been reported to be lower in people with Colitis who smoke.

    However, not all studies agree with this. One study found that people with Colitis who smoked had an increased risk of developing joint and skin problems. A study that analysed data from 16 previous studies found no difference in risk of colectomy, flare-ups or pouchitis in those with Colitis who smoked, compared to those who didn’t.

    It is important to consider the harmful effects of smoking. Smoking is a known cause of at least 13 types of cancer, including bowel, lung, stomach and ovarian. Smoking is also a known cause of cardiovascular disease – with smokers almost twice as likely to have a heart attack compared to those who have never smoked. In general, health professionals consider that the risks of smoking greatly outweigh any benefits seen in Colitis, and strongly discourage smoking in everyone, whether or not they have Crohn's or Colitis.

    Why may smoking have a protective effect against Ulcerative Colitis?

    We don’t really understand why smoking has a protective effect against Colitis. There are many chemicals in cigarettes that could be contributing to this effect. Nicotine is the most widely studied and is likely to be having an impact.

    People with Colitis may have a thinner mucus layer in the colon and rectum when compared to healthy people. Nicotine may increase the production of this mucus. Nicotine may also suppress the immune system and prevent inflammation in the colon. Another theory is that nitric oxide, released by nicotine, may reduce muscle activity in the colon and so reduce the need to go the toilet urgently.

    We know that the genes a person has inherited can contribute to developing Colitis. Smoking can change how a person’s genes are expressed – providing another potential mechanism for how smoking may influence the development of Crohn's or Colitis.

    So do I need to give up smoking?

    It may be tempting to continue or even take up smoking to help your Colitis. However, research findings on smoking and Crohn's or Colitis are mixed. We know that smoking increases your risk of chronic bronchitis, lung cancer, other cancers and heart diseases, and is not recommended by health professionals, even for people with Colitis. There are many treatments that are much safer than smoking that can be explored. For more information on drug therapies, please see our treatment information and our information on Other treatments for IBD.

    Can nicotine replacement therapy help Colitis?

    Some people have found that using nicotine replacement therapies, such as nicotine patches or chewing gum, is helpful in managing their Colitis. Results from research studies are inconclusive. This may be because other elements of cigarette smoke could be contributing.

    The use of nicotine patches in people with mild or moderately active Colitis has been shown to be more effective than a placebo (a blank patch with no nicotine) in inducing remission. However, nicotine isn’t more effective than conventional Crohn's or Colitis drug treatments, such as aminosalicylates (5-ASAs) and steroids, in inducing remission. It is not yet known whether nicotine is more effective as a therapy in those who are ex-smokers compared to those who have never smoked. Although nicotine replacement therapies are much safer than smoking, not everybody can tolerate nicotine. Nicotine is highly addictive – and can have other effects, such as increasing heart rate and blood pressure. In several studies, people who tried nicotine therapy for Crohn's or Colitis suffered side effects such as dermatitis, nausea, headaches or sleep disturbance.

    As yet, there has been no research into the effect of electronic cigarette usage on Ulcerative Colitis. Public Health England has reported that e-cigarettes are 95% less harmful than smoking cigarettes. However, e-cigarettes are only recommended for those who wish to give up smoking, or reduce the amount they smoke, rather than by people who want to start smoking.

    If you wish to try a nicotine replacement therapy, discuss it with your specialist doctor or IBD team.

    With the money I saved, I treated myself to a new laptop. I felt that it was important to treat myself in recognition of giving up what had been a major habit in my life.

    Diagnosed with Crohn's Disease in 2012

  • Can I get help to give up smoking?

    The NHS has a programme to help people stop smoking. For more information see Your doctor or any other healthcare professional should also be able to help you. Some pharmacists, private health insurers, employers and local governments offer programmes to help you stop smoking.

    If you have Colitis and are interested in giving up smoking, you are advised to discuss this with your IBD team. Some people with Colitis may find that their symptoms worsen when they stop smoking, so it could be helpful to have a plan in place in case this happens.

    The NHS can help with nicotine replacement therapy (NRT), which includes patches, gum, lozenges and inhalers. NRT gets nicotine into the bloodstream without smoking and its harmful side effects. Medicines such as bupropion or varenicline can be used to manage withdrawal symptoms.

    You may like to consider including counselling as part of your programme to stop smoking. Research has found that a combination of medication and counselling can be more effective than a single approach.

    I was a smoker for 30 years, but when I was diagnosed with Crohn’s, my consultant advised me to give up. I tried, and managed to give up after a bowel resection operation. 

    Diagnosed with Crohn's Disease in 2012

  • Help and support from Crohn's & Colitis UK
    We offer information on many aspects of Crohn’s DiseaseUlcerative Colitis and other forms of Inflammatory Bowel Disease. You may be interested in our information on:

    Health professionals can order some publications in bulk by using our online ordering system. If you would like a printed copy of any of our information, please contact our helpline.

    Our helpline is a confidential service providing information and support to anyone affected by Crohn's or Colitis. Our team can:

    • Help you understand more about Crohn's or Colitis, diagnosis and treatment options
    • Provide information to help you to live well with your condition
    • Help you understand and access disability benefits
    • Be there to listen if you need someone to talk to
    • Help you to find support from others living with the condition

    Call us on 0300 222 5700


    Use our LiveChat 

    Crohn’s & Colitis UK forum

    This closed-group community on Facebook is for everyone affected by Crohn's or Colitis. You can share your experiences and receive support from others.

    Crohn’s & Colitis UK patient panels

    Patient panels, which are supported by Crohn’s & Colitis UK, are groups of people with Crohn's or Colitis who use their perspective as a patient to work with their IBD team to help improve their hospital services. For more information on patient panels, please contact our Patient Engagement Team.

    Crohn’s & Colitis UK Local Networks

    Our Local Networks of volunteers across the UK organise events and provide opportunities to get to know other people in an informal setting, as well as to get involved with educational, awareness-raising and fundraising activities. You may find just being with other people and realising that you are not alone can be reassuring. Families and relatives may also find it useful to meet other people with Crohn's or Colitis. All events are open to members of Crohn’s & Colitis UK

  • Other useful organisations

    NHS Stop Smoking Services by area:


    Northern Ireland





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We know it can be difficult to live with, or support someone living with these conditions. But you’re not alone. We provide up-to-date, evidence-based information and can support you to live well with Crohn’s or Colitis.

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