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Crohn's disease

Medically reviewed by Last updated on Mar 15, 2023.

What is Crohn's disease?

Harvard Health Publishing

Crohn's disease is an inflammatory bowel disease in which inflammation injures the intestines. It is a long-term (chronic) condition. Crohn's disease typically begins between ages 15 and 40.

No one knows for sure what triggers the initial intestinal inflammation at the start of Crohn's disease. A viral or bacterial infection may start the process by activating the immune system in the intestine. However, the immune system attack is not turned off: it stays active and creates inflammation even after the infection goes away.

Certain genes passed on from parent to child increase the risk of developing Crohn's disease, if the right trigger occurs.

Once Crohn's disease begins, it can cause lifelong symptoms that come and go. The inner lining of the intestine thickens, and can wear away. The deeper layers of the intestine also become inflamed. This creates ulcers, cracks and fissures. Inflammation can allow an abscess (a pocket of pus) to develop.

A common complication of Crohn's disease is called a fistula. A fistula is an abnormal connection between two areas of the body; in Crohn's disease, the most common type is between two parts of the digestive tract, usually between one part of the intestine and another. A fistula can be created after inflammation becomes severe.

The section of the small intestine called the ileum is especially prone to damage from Crohn's disease. The ileum is located in the right lower abdomen. However, ulcers and inflammation can occur in all areas of the digestive tract, from the mouth to the rectum.

A few other parts of the body, such as the eyes and joints, also can be affected by Crohn's disease.

Crohn's disease

Symptoms of Crohn's disease

Some people with Crohn's disease have only occasional cramps, or diarrhea. Their symptoms are so mild they do not seek medical attention.

However, most people with Crohn's disease have more bothersome symptoms. They may experience long stretches of time with no symptoms. But these are interrupted by flare-ups of symptoms.

When Crohn's disease first begins, or during a flare-up, you might experience:

Diagnosing Crohn's disease

If you have Crohn's disease, your symptoms and the results of various tests will usually fit a pattern over time that is highly suggestive of the diagosis. Even so, it may require months for your doctor to diagnose Crohn's disease with certainty.

Your doctor will look for evidence of intestinal inflammation. He or she will try to distinguish it from other causes of intestinal problems such as infection or ulcerative colitis. Ulcerative colitis is another disease that, like Crohn's diseases, also causes intestinal inflammation.

Test abnormalities that are often, but not always, found in people with Crohn's disease include:

Treatment options

The following list of medications are related to or used in the treatment of this condition.

View more treatment options

Expected duration of Crohn's disease

Crohn's disease is a lifelong condition. But it is not continuously active.

Following a flare-up, symptoms can stay with you for weeks or months. Often these flare-ups are separated by months or years of good health without any symptoms.

Preventing Crohn's disease

There is no way to prevent Crohn's disease.

But you can keep the condition from taking a heavy toll on your body. Maintain a well-balanced, nutritious diet to store up vitamins and nutrients between episodes or flare-ups. By doing so, you can decrease complications from poor nutrition, such as weight loss or anemia.

Also, do not smoke. Along with many other harmful health effects, smoking is a risk factor for developing Crohn's disease and is also linked to complications such as fistulas.

Crohn's disease can increase your risk of getting colon cancer. Have your colon checked regularly for early cancerous or precancerous changes. Check with your doctor regarding which types of tests to have and how frequently to repeat them.

Treating Crohn's disease

Medications are very effective at improving the symptoms of Crohn's disease. Most of the drugs work by preventing inflammation in the intestines.

For mild disease, steroids and/or anti-inflammatory drugs called aminosalicylates (such as mesalamine or sulfasalazine) are usually tried first. Aminosalicylates are chemically related to aspirin. They suppress inflammation in the intestine. They are given either as pills by mouth or by rectum, as an enema. Certain antibiotics help by killing bacteria in irritated areas of the bowel if infection is suspected or confirmed.

Antidiarrheal medications such as loperamide (Imodium) may be helpful if you have diarrhea.

Other more powerful anti-inflammatory drugs, such as azathioprine or 6-mercaptopurine, may be helpful. But they can also suppress your immune system, increasing your risk of infections. For this reason, they are not often used on a long-term basis.  Combinations of these and some of the newer medications described below are commonly recommended.

Among the newest drugs approved for treatment of Crohn's disease are tumor necrosis factor (TNF) inhibitors and other injectable treatments. TNF is a substance made by immune system cells that causes inflammation. TNF inhibitors have potentially very serious side effects. They are generally prescribed for moderate to severe Crohn's disease that is not responding to other therapies and may be taken in combination with other medications. Adalimumab (Humira), certolizumab pegol (Cimzia), and infliximab (Remicade) are TNF inhibitors that have been found to improve Crohn's disease. When TNF inhibitors are not effective, other injectable options include ustekinumab (Stelara), risankizumab (Skyrizi), and vedolizumab (Entyvio).

Surgery to remove a section of the bowel is another possible treatment. In general, surgery is recommended only if a person has

When to call a professional

New or changing symptoms often mean that additional treatment is needed. People who have Crohn's disease should be in frequent contact with a doctor.

One serious complication is bowel obstruction. This occurs when the intestine becomes so narrowed that the digestive contents cannot pass through. Bowel obstruction causes vomiting or severe abdominal pain. It requires emergency treatment.

Other symptoms that require a doctor's immediate attention are:


Crohn's disease can affect people very differently. Many people have only mild symptoms. They do not require continuous treatment with medication.

Others require multiple medications and develop complications. Crohn's disease improves with treatment. It is not usually a fatal illness. While it can be controlled in most cases, it cannot be cured.

Crohn's disease requires people to pay special attention to their health needs and to seek frequent medical care. But it does not prevent most people from having normal jobs and productive family lives.

It can be helpful for a newly diagnosed person to seek advice from a support group of other people with the disease.

Additional info

Crohn's and Colitis Foundation of America

National Institute of Diabetes and Digestive and Kidney Disorders

Learn more about Crohn's disease

Treatment options guides (external)

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.