How Does Smoking Affect Crohn's Disease?

Medically Reviewed by Minesh Khatri, MD on May 29, 2024
5 min read

Your doctor can give you a long list of reasons to quit smoking. By kicking the habit, you'll lower your risk for cancer, lung disease, heart disease, and stroke, along with many other life-shortening diseases. Quitting will also help you avoid severe symptoms and complications of Crohn's disease.

Smoking doesn't cause Crohn's disease. Genes and a problem with the immune system are to blame for this type of inflammatory bowel disease (IBD). But smoking can increase your chance of getting Crohn's disease, and it could make the disease more severe and harder to treat.

Quitting might seem impossible, especially if you've smoked for many years and have tried before. But giving up smoking can bring big improvements in your Crohn's symptoms and your health in general.

Crohn's disease is one type of IBD. Ulcerative colitis is the other type. Smoking has very different effects on each of these diseases.

In ulcerative colitis, cigarette smoking seems to offer some protection against symptom flare-ups (although that's not a reason to start smoking because it has so many other health risks). The opposite is true for Crohn's disease.

Smokers are about two to five times more likely than nonsmokers to develop Crohn's disease, and their disease gets worse faster. Heavy smokers have more severe Crohn's disease than light smokers.

Smoking has a bigger effect on Crohn's disease in certain groups of people. If you were assigned female at birth or Crohn's is in your ileum – the last part of your small intestine – smoking could make the disease more severe.

Doctors don't know exactly how smoking affects Crohn's disease, but they have a few ideas.

Reactive oxygen species. The chemicals you breathe in with each puff of smoke increases your body's production of reactive oxygen species (ROS). These unstable molecules, also called free radicals, damage cells in your GI tract and other parts of your body. The chemicals in cigarette smoke also make it harder for your cells to fix damage when it happens.

Problems with the immune system. Smoking can damage your immune system to the point where it doesn't work as well as it should. Crohn's is caused by a flawed immune response that makes your immune system misfire and attack your intestines.

A weak barrier. Your intestines come equipped with a wall of cells and a layer of mucus to protect them against damage. Smoking weakens this barrier.

Slow healing. Smoking reduces blood flow to your tissues and slows the healing process. That makes it harder for your body to fix any damage from Crohn's disease in your GI tract.

Gene changes. Smoking might cause permanent changes to genes in your colon. These genetic changes could affect your immune system and make it easier for the chemicals in cigarette smoke to damage cells in your intestine.

The use of electronic cigarettes, or e-cigarettes has skyrocketed in recent years, especially among young people. The use of e-cigarettes, called vaping, is sometimes promoted as a safer alternative to tobacco, but it does have risks.

So far, studies haven't shown that vaping has a negative effect on Crohn's disease. E-cigarettes may be less harmful than tobacco cigarettes, but they're still pretty new. We need more studies to confirm whether or not they're risky for people with Crohn's disease.

Because vaping has other negative health effects, like lung damage, you're safer not starting.

People who smoke have more severe Crohn's disease symptoms and more relapses. Smoking doesn't change how Crohn's disease medicine works, but it might make treatment less effective at putting the disease into remission.

People who smoke have about double the number of Crohn's relapses as nonsmokers. They're also more likely to need medicines or surgery.

After surgery, there's a greater chance Crohn's disease will come back if you smoke. This is called a recurrence. Within 1 year after resection surgery to remove part of the small intestine and colon, 70 percent of smokers had damage in their intestine again, compared to 35 percent of nonsmokers.

Quitting smoking is one of the best things you can do to manage Crohn's disease. It's as effective as immunotherapy drugs at managing Crohn's symptoms and putting the disease into remission.

Within 6 months after you stop smoking, your risk of having a Crohn's disease relapse or flare-up drops. Within 2 years after you quit, your disease won't be any worse than that of a nonsmoker.

It's not easy to quit smoking. If it were, everybody would have done it already. The highly addictive quality of nicotine makes it hard to stop. When you do try to quit, withdrawal symptoms like restlessness and anxiety can make you start right back up again.

You'll have better odds of quitting smoking and staying off cigarettes if you get some help from your doctor and a combination of these methods:

Counseling. Your doctor or a smoking cessation counselor can give you advice on ways to quit and how to deal with cravings when they strike.

Nicotine replacement therapy (NRT). Nicotine is the addictive chemical that makes you want to keep smoking. NRT relieves cravings and prevents withdrawal symptoms to make it easier to quit. It comes in patches, sprays, gum, inhalers, or lozenges. The patch can be helpful if you're a heavy smoker or you've had a lot of trouble quitting.

Medicine. Varenicline (Chantix) blocks the effects of nicotine on your brain. Bupropion (Wellbutrin) reduces withdrawal symptoms to help you quit. These medicines work better when you use them together with education and counseling.

Not everyone is able to quit on the first try or at all. If you can't stop smoking, make sure your doctor monitors your Crohn's disease and overall health more closely. You may need more intense treatment with biologic drugs or other medications to keep your disease under control.