Irritable bowel syndrome (IBS) is considered a functional bowel disorder, not an autoimmune disease. However, certain autoimmune diseases produce symptoms similar to IBS and you can have an autoimmune disease and IBS at the same time.

Let’s take a closer look at the connection between autoimmune diseases and IBS, and why it matters when seeking a diagnosis.

Your immune system defends you from foreign invaders, such as:

  • bacteria
  • fungi
  • toxins
  • viruses

When it senses something foreign, it sends an army of antibodies on the attack. This can help prevent sickness or lessen the severity of symptoms. In some cases, it can even prevent future sicknesses from those same invaders.

If you have an autoimmune condition, it means your immune system is mistakenly attacking your body like it’s those foreign invaders.

It sees certain healthy cells as foreign. The immune system response leaves you with inflammation and damage to healthy cells.

Symptoms depend on what part of the body is affected.

Autoimmune conditions usually involve periods of intense disease activity. These are followed by remissions during which you have fewer symptoms.

There are more than 100 autoimmune diseases affecting every part of the body, including the gastrointestinal tract.

In a functional bowel disorder, the gastrointestinal tract (GI) doesn’t work as it should, but there’s no obvious abnormality.

Functional bowel disorders include:

  • IBS
  • functional constipation: fewer than three bowel movements per week or incomplete bowel movements
  • functional diarrhea: recurrent loose or watery stools not associated with abdominal pain
  • functional bloating: abdominal distention not associated with another disorder

Some things that can affect the GI tract are:

  • antacids that contain calcium or aluminum
  • certain medications, such as antidepressants, narcotics, and iron pills
  • changes to routine, such as travel
  • a diet low in fiber
  • a diet rich in dairy products
  • frequent use of antacids
  • holding in bowel movements
  • lack of physical activity
  • pregnancy
  • stress

Recent research suggests a possible link between IBS and autoimmune disorders. It may be that having an autoimmune disease can increase the risk of IBS.

More research is needed before this can be confirmed.

Systemic autoimmune diseases are linked to inflammation and can cause symptoms associated with IBS. This can be due to:

  • the disease itself
  • medication used to treat the disease
  • IBS as an additional primary disorder

The following are some autoimmune diseases that can cause symptoms similar to IBS:

Lupus erythematosus

Systemic lupus erythematosus (SLE) causes a variety of symptoms, depending on the part of the body that your immune system is attacking. Symptoms generally include:

GI symptoms are also common in SLE, and can include:

  • abdominal pain
  • constipation
  • vomiting

Rheumatoid arthritis

Rheumatoid arthritis causes joint damage throughout the body. Symptoms include joint pain and swelling.

Gastrointestinal problems are common as well and include:

Ankylosing spondylitis

Ankylosing spondylitis is a type of arthritis that affects the spine. Symptoms may include:

  • fatigue
  • loss of appetite or weight loss
  • poor posture and stiffness

Ankylosing spondylitis can also cause inflammation of the bowels. Coexisting conditions can include ulcerative colitis and Crohn’s disease.

Sjögren syndrome

Sjögren syndrome affects the salivary glands and tear sacs (lacrimal glands). Symptoms usually include:

  • dry eyes
  • dry mouth
  • swallowing difficulty

It can also affect the entire GI tract, which can cause:

  • dyspepsia (indigestion)
  • esophageal atrophy
  • nausea

Behcet’s disease

Behcet’s disease affects veins and blood vessels throughout the body. It can also cause GI lesions and other GI symptoms such as:

  • abdominal pain
  • anorexia
  • diarrhea or bloody diarrhea
  • nausea
  • ulcers within the digestive tract

Progressive systemic sclerosis (scleroderma)

Scleroderma is a condition in which the body produces too much collagen, which can lead to:

  • impaired taste
  • restricted movement
  • skin thickening and tightening
  • thinning of the lips
  • tightness around the mouth, which can make it hard to eat

GI symptoms may include:

  • bloating
  • constipation
  • diarrhea

To understand whether you have IBS or an autoimmune disorder, your doctor will want to know your personal and family medical history. This includes an overview of:

  • medications you take
  • recent infections or illnesses
  • recent stressors
  • previously diagnosed health conditions
  • foods that may calm or aggravate symptoms

Your doctor will start with a basic physical examination.

Blood and stool tests are used to check for infections and other diseases. The results, plus your symptoms and medical history, will guide any further diagnostic testing. This may include a colonoscopy or imaging tests.

Autoimmune diseases that mimic IBS should be ruled out

There’s no specific test for IBS. The diagnosis depends on a pattern of symptoms.

You may receive a diagnosis of IBS if:

  • you’ve had symptoms of IBS, such as bloating, abdominal discomfort, or a change in bowel movements and habits for more than 3 months
  • you’ve had symptoms on and off for at least 6 months
  • your quality of life is affected
  • no other reason can be found for your symptoms

The cause of IBS isn’t entirely clear. It may be a combination of factors that cause the disorder. It may even be that they’re different for everyone.

Some factors that may play a role are:

  • stressful events or prolonged periods of stress
  • mental health disorders such as anxiety or depression
  • bacterial or viral infections of the GI tract
  • bacterial overgrowth or changes in gut bacteria
  • inflammation in the intestines
  • food sensitivities or intolerances
  • variations in muscle contractions in the intestine

IBS is not classified as an autoimmune disease, but as a functional bowel disorder. Researchers continue to explore the association between IBS and autoimmune disorders.

Some autoimmune diseases and their treatments cause many of the same symptoms. It’s also possible to have IBS at the same time as an autoimmune disease.

Because of these overlaps, certain autoimmune diseases should be ruled out as you seek a diagnosis for IBS.