Immune System Suppressors

There is no cure for Crohn’s disease, so symptom relief comes in the form of remission. A variety of treatments are available that can help ease your symptoms. Immunomodulators are drugs that modify the body’s immune system. For someone with Crohn's, this can help reduce the swelling that causes so many symptoms.

Immunomodulators include drugs that are immunosuppressants and immunostimulants. Immunosuppressants inhibit the body’s immunity, but immunity suppression can also put the body at higher risk for other diseases.

Immunostimulants increase or “stimulate” the body’s immune system, which encourages the body to begin fighting illness.

There are various types of immunomodulators, each sold under its own brand name. Azathioprine, mercaptopurine, and methotrexate are the three main types.


Azathioprine is often used in people who receive an organ transplant to prevent the body from rejecting the new organ by suppressing the body’s immune system. It is also used to treat rheumatoid arthritis, which is a condition where a person’s body attacks their own joints.

Azathioprine has been found to reduce the risk of recurrence of Crohn’s flare-ups over a six month to two-year period. Research published in the journal Gut has also shown that azathioprine may reduce the need for steroid treatment. This is an important discovery because steroids can cause uncomfortable side effects. However, the long-term effects have not yet been proven in research.

There are also some rare, but severe, side effects of azathioprine. This drug causes your body to produce fewer white blood cells. This can cause problems because white blood cells fight infection. People taking azathioprine may also experience an inflammation of the pancreas or a higher risk of developing lymphoma.

Because of these side effects, azathioprine is usually only prescribed for the more severe cases of Crohn's. You should consider all of the risks before taking azathioprine.


Mercaptopurine is known to stop cancer cells from growing. This drug is often used to treat leukemia. In people with Crohn’s, mercaptopurine can induce remission.

Mercaptopurine can reduce the production of white and red blood cells. Your physician will likely want to conduct regular blood tests to ensure there is no damage to your bone marrow. You may also be tested for TPMT deficiency, which is an enzyme deficiency that could decrease the number of cells responsible for providing immunity.

Other side effects of mercaptopurine can include:

  • mouth sores
  • fever
  • sore throat
  • blood in the urine or stool

You should consider all possible side effects before you start treatment.


Methotrexate blocks cell metabolism, which causes cells to die. This has lead to its use for Crohn's disease, cancer, and psoriasis. However, methotrexate has side effects that include possible toxicity of the liver or bone marrow and, in rare cases, toxicity of the lungs. Men or women attempting to get pregnant should not use this drug. Less severe side effects include:

  • headache
  • drowsiness
  • skin rash


Levamisole is an immunostimulant that helps the body’s natural immune system fight disease. It is often used in cancer treatments, but in trials it’s been studied in treating people with Crohn's disease. Research published in the Journal of Gastroenterology suggests that the side effects of levamisole may keep it from being a common treatment of Crohn’s disease. It was found in a study reported in the British Medical Journal to cause two people to develop a form of temporary arthritis that resolved after they stopped taking the medication.

BCG Vaccine

Known for its use against tuberculosis, the BCG vaccine has been studied as a possible treatment for Crohn’s disease. However, according to a study reported in the journal Gut, research has not yet proved that it is helpful for every person with Crohn’s. While generally well tolerated by people in clinical studies, the Journal of Crohn's and Colitis published a case report in which the vaccine, when used to treat Crohn’s disease in a pregnant woman, was found to cause death in a woman’s newborn baby.

Things to Keep in Mind

Immunomodulators can help combat symptoms related to Crohn's disease, but they interfere with your body’s ability to fight infection. While taking immunomodulators, pay attention to any signs of infection, such as fever or chills. If you develop these symptoms, contact your doctor immediately.

Any time you are taking immunomodulators, be sure to get your blood tested regularly for signs of damage to your bones and internal organs.

Some immunomodulators may be OK to take during pregnancy, but you should not start a new medication during pregnancy. You should talk to your doctor if you are pregnant or may become pregnant. This applies to both men and women participating in conception.