Irritable bowel syndrome (IBS) is a common, long-term disorder that affects the large intestine (bowel or colon). It can cause abdominal pain, cramps, bloating and bouts of diarrhoea or constipation. IBS affects around 15 per cent of Australians and is more common in women than in men.

IBS tends to appear in people aged in their twenties, although it may develop in younger and older people. It is unusual for IBS to first appear in someone aged over 40 years.

IBS does not cause permanent damage to the digestive tract or lead to serious disease, such as cancer.

What are the symptoms of IBS?

The symptoms of IBS may vary from person to person. Symptoms tend to come and go over time, and often last for several days or weeks. There may be times when symptoms are worse than others.

Common symptoms of IBS include:

  • Abdominal pain and cramps.
  • Abdominal bloating.
  • Diarrhoea and/or constipation (sometimes these may alternate).
  • Excessive flatulence (wind).
  • Mucus in the stool.
  • Urgent need to go to the toilet.
  • Feeling of not having completely emptied the bowels after going to the toilet.

The symptoms of IBS are often relieved by a bowel movement (passing stool).

What symptoms are not caused by IBS?

If a person notices bleeding from the back passage, blood in the stool, fever, weight loss or severe diarrhoea at night, it is important to see a doctor for further assessment. These symptoms are not caused by IBS and may indicate a more serious condition.

A person should also see a doctor if their symptoms get progressively worse, stools are pale, bulky, very offensive smelling and difficult to flush away (this may indicate a problem with absorbing fat), or if they are concerned about their symptoms.

What causes IBS?

The exact cause of IBS is unknown, but experts think that several factors may be involved. These include:

  • Problems with digestion: the muscles of the intestines work to squeeze food through the digestive system. In people with IBS, this process may not be working properly, so that food moves through the digestive system too slowly or too quickly. If it moves too slowly it can lead to constipation; if it moves too quickly it may cause diarrhoea.
  • Overactivity of the nerves in the intestines: if the nerves in the digestive system are oversensitive, they may cause people to feel more pain. This oversensitivity may cause the crampy abdominal pain associated with IBS.
  • Gastrointestinal infections: some people develop IBS after a gastrointestinal infection.
  • Genetic and early life factors: close relatives of a person with IBS may be more likely to develop IBS themselves; some early childhood experiences (e.g. poor nutrition) may also be involved in the development of IBS.

IBS is not caused by a blood or biochemical disorder.

What triggers IBS?

Triggers (things that bring on an episode of IBS) vary from person to person. The most common triggers include:

  • Certain foods and drinks (these vary widely and include fizzy drinks, alcohol, drinks containing caffeine, chocolate, beans, cabbage, dairy products, spices, fruits, fatty or fried food).
  • Eating too quickly or too much.
  • Stress and anxiety.
  • Hormonal changes (e.g. some women have IBS just before, or during, their menstrual period).
  • Gastrointestinal infection.

It is important that people try to identify their own triggers so that they can avoid or minimise IBS symptoms.

How is IBS diagnosed?

The diagnosis of IBS can be challenging, because the symptoms are also seen in other digestive conditions. There is no one test that can show whether a person has IBS. A doctor will usually base the diagnosis on a person’s symptoms and the elimination of other causes. Sometimes investigations such as blood tests may be done to rule out other conditions.

To help the process of diagnosis, experts have developed set of criteria to help determine if a person has IBS. One example is the Rome criteria – this definition says that a person with IBS will have had abdominal pain and discomfort that lasts for at least 3 days a month in the last 3 months, plus 2 or more of the following:

  • Improvement of symptoms with a bowel movement.
  • Altered frequency of bowel movements (e.g. going to the toilet more or less often).
  • Altered consistency of stool (e.g. softer, harder).

Managing IBS

IBS can usually be managed with diet and lifestyle modifications, including stress management, getting enough sleep and exercise. It can also be helpful to keep a diary of events surrounding each episode to help identify things that may trigger IBS symptoms or make them worse, such as trigger foods.

Irritable bowel syndrome treatment focusses on diet and lifestyle changes, as well as medicines.

Last Reviewed: 21/04/2016



1. Mayo Irritable bowel syndrome (revised July 2014). Accessed March 2016. 2. Gastroenterological Society of Australia (GESA); Digestive Health Foundation (DHF). Irritable bowel syndrome (IBS). Accessed March 2016. 3. NHS Choices. Irritable bowel syndrome (IBS) (reviewed September 2014). Accessed March 2016. 4. eTG Complete. Irritable bowel syndrome (revised February 2011). Therapeutic Guidelines Pty Ltd; Melbourne. Accessed March 2016.