Irritable Bowel Syndrome

What is irritable bowel syndrome?

Irritable bowel syndrome (IBS) is a functional disorder diagnosed by the presence of gastrointestinal symptoms including diarrhea, constipation, gas, cramping and abdominal pain. Different people, though, will experience different clusters of symptoms, thus requiring varying treatments. IBS can be a long-term condition requiring careful management, and it is often addressed with a combination of lifestyle and dietary changes, as well as pharmaceutical interventions in chronic cases.

IBS vs. IBD, Crohn’s disease and ulcerative colitis

IBS does not cause inflammation or permanent damage such as bleeding or ulcers, nor increased risk of cancers, unlike the often-confused inflammatory bowel disorder (IBD). IBD is a more serious digestive condition, including chronic diseases such as ulcerative colitis, which affects the large intestine, and Crohn’s disease, which can affect the entire digestive tract and deeply affect the walls of the intestines.

IBS is diagnosed by considering recurrence of symptoms over the long-term, and unlike IBD it cannot be diagnosed based on physical examination or by looking at the bowel during colonoscopy.

Irritable bowel syndrome symptoms

The appearance of different symptoms determines the diagnosis of different kinds of IBS. Some people mainly experience diarrhea (IBS-D), some mainly experience constipation and painful abdominal cramps (IBS-C), while some experience both constipation and diarrhea at different times, which is called mixed IBS (IBS-M). Other people have diverse symptoms, which are categorized as unsubtyped IBS (IBS-U).

Abdominal Pain

Abdominal cramping, particularly felt in the lower belly, is one of the most common symptoms of IBS. They typically increase after meals, and are relieved by a bowel movement. These painful spasms indicate the passage of food through the digestive tract, either too quickly (as diarrhea) or too slowly (constipation).

Bloating and Gas

Intense bloating and gas is another common symptom of IBS. Some people may experience increased burping.


Some people experience diarrhea as a primary symptom of IBS, passing loose, watery stools more than three times per day. The urge to defecate may be difficult to control and can impact a person’s daily life. Diarrhea may occur in alternating patterns with periods of constipation.


Constipation and associated painful abdominal cramping is another common symptom of IBS. This may mean passing fewer than three bowel movements per week, or straining and feeling as though not all stool can be passed. When it is passed, stool is often small and hard.

Mucus or Blood in Stool

Appearance of mucus in the stool is a common symptom of IBS. Those passing blood in their bowel movements, however, should see a doctor, as this may be indicative of more serious issues such as Crohn’s disease or colon cancer.

Food Intolerance and Allergies

IBS sufferers commonly experience food intolerance, an unpleasant reaction to food involving cramps, fluid or gas and bloating. These reactions are different from a food allergy, and are the gut’s reaction to the food ingested. Foods commonly causing intolerance include: Wheat; dairy; fatty, creamy or fried foods; alums such as garlic or onions; stone fruits and other kinds of fruit; brassicae such as cabbage, cauliflower or Brussels sprouts; pulses such as lentils or beans and chili peppers.

Though it is far less common, some IBS sufferers, particularly those with IBS-D, may have food allergies. These allergies should be assessed and diagnosed by a specialist. Allergies are most commonly a factor in IBS when the person also experiences hay fever, eczema or asthma.

When to see a Doctor?

Though many people manage IBS on their own, some symptoms should be evaluated by a doctor. Symptoms like weight loss, rectal bleeding or nighttime cramping might be indicative of a more serious issue.

Causes of IBS

IBS is a functional disorder, which means it is diagnosed through changes in the function of the digestive system. This may be linked to a fault in communication between the brain and the digestive tract, or unusual activity of the colon or small intestines. These changes could be caused by several factors, including food sensitivity, infection or bacterial overgrowth. An individual’s psychological condition, hormone changes or stress levels are other possible causes.

Food Sensitivities

An individual may experience IBS due to an intolerance of foods such as wheat; dairy; fatty, creamy or fried foods; alums such as garlic or onions; stone fruits and other kinds of fruit; brassicae such as cabbage, cauliflower or Brussels sprouts; pulses such as lentils or beans and chili peppers. These may relate to a compromised ability to absorb fats, sugars or acids.

Infection and Bacteria

Infections such as gastroenteritis (commonly called the stomach flu) can cause symptoms of IBS. Other bacterial overgrowth, such as small intestine bacterial overgrowth (SIBO) or salmonella infection may be a cause – though salmonella infection can be life-threatening and should be treated by a medical professional. Though not as severe as an overgrowth, changes to the balance of normal gut bacteria may be a cause of IBS.

Individual Factors

IBS is often linked to psychological factors such as stress, anxiety or depression, and stress management is one possible treatment tool. Some people also experience more intense pain from gas trapped in the belly during digestion, which can cause IBS symptoms.

Neurotransmitters or reproductive hormones may be imbalanced in some IBS sufferers. This can be affected by changes to an individual’s hormones, such as throughout the menstrual cycle.

Genetics may be a cause of IBS, but there is limited evidence to support this.

Irritable bowel syndrome treatments

Lifestyle changes

Unlike IBD, IBS is often managed with lifestyle changes, and these are often the first approach to treatment. Lifestyle changes may address factors of diet or stress, though these vary from person to person, since each case of IBS is stimulated by different factors.

Stress and anxiety treatments

Doctors once believed that IBS was caused by stress, and although the causes are now seen as more varied, addressing stress and anxiety is a common treatment approach. Some people do not experience generalized anxiety or stress, but do experience anxiety and extreme vigilance around their IBS symptoms and gastrointestinal functions (known as GI symptom-specific anxiety). People with this kind of anxiety often limit their exposure to activities and situations that would be affected by their IBS, which can create a vicious cycle of building anxiety and stress, thus increasing symptoms. Behavioral therapy, like cognitive behavioral therapy, psychotherapy, relaxation therapy, biofeedback and hypnotherapy, may be used to help individuals both manage general stress and anxiety and break the cycle of GI symptom-specific anxiety.

Self-care to manage stress is another option, with common techniques including meditation, yoga and exercise.

IBS and diet

Each person has different dietary triggers for IBS, and a healthcare professional can help a person narrow down their specific issues, often with the help of a food diary to find connections between specific foods and symptoms.

If sensitivity to specific foods is a trigger for IBS symptoms, reducing or eliminating these foods from the diet is a treatment method. This is one of the simplest dietary changes. Another potential treatment is to eat smaller, more frequent meals, if large meals are trigger a person’s symptoms. Eating more slowly can reduce gas and bloating.

Foods commonly associated with abdominal cramping or diarrhea include coffee, caffeine, alcohol or high-fat foods, as well as poorly-digested sugars, such as sorbitol or fructose. Beans, raisins or breads can cause gas. Lactose intolerance can trigger IBS symptoms.

Eating a high-fiber diet can improve stool quality and keep the GI tract healthy. However, a diet with an excessive amount of fiber can also cause gas and diarrhea.


Studies have indicated that reducing consumption of FODMAPs (Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols) is an effective approach. These foods cannot be easily absorbed by the small intestine and so increase fluid in the bowel. They are also easily fermented by colonic bacteria, increasing gas and bloating. The increased fluid and gas makes all foods require more time for digestion, causing pain and diarrhea.

Irritable bowel syndrome medications

Mild to moderate cases of IBS can usually be treated with diet and lifestyle changes, as well as stress management techniques. Medications are available for the treatment of moderate to severe IBS that does not improve in response to these changes.

Anti-diarrheal medications

Over the counter medications like loperamide (Imodium) are often used to treat IBS, and can decrease urgency and frequency of bowel movements. Common prescriptions drugs include diphenoxylate (Lomotil, Lomocot) and atropine. These drugs decrease the frequency of intestinal movement, thus allowing the stool to stay in the intestine longer and absorb more water, improving its form. They do not affect abdominal pain or cramping, though, and may cause or worsen constipation, making them inappropriate for IBS sufferers who experience constipation.

Atropine and diphenoxylate can be addictive, and their side effects can include itching, dizziness, nausea, vomiting or drowsiness. Loperamide can cause abdominal pain, vomiting, nausea or dizziness, though these effects do not usually last long.

Bile acid binders like cholestyramine (Prevalite), colestipol (Colestid) or colesevelam (Welchol) benefit some people, though they may cause bloating.

These medications are not appropriate for people with IBD or intestinal infections. If a patient has severe diarrheal symptoms, such as blood in their stool, they should not take these medications.

Anticholinergic and antispasmodic medications

Antispasmodic medications such as dicyclomine (Bentyl) and hyoscyamine (Levsin) are commonly prescribed to decrease painful abdominal spasms. Antispasmotics prevent muscle contractions, while anticholinergics block acetylcholine’s effect in smooth muscle, secretory glands and the central nervous system. Both make bowel movements less urgent and painful. Smooth muscle relaxants, such as alverine, mebeverine and peppermint oil may also be used.

However, few studies have indicated that these drugs are effective for most IBS sufferers. They can also increase constipation and cause side effects, such as heartburn, difficulty urinating, constipation and dry mouth. These medications are not appropriate for all people with IBS, particularly if they have other intestinal issues, and should be taken under a doctor’s supervision.

Antidepressant medications

Antidepressant medications can treat IBS in two ways – as a treatment for depression, which is commonly associated with chronic disorders, and by affecting the connection between the brain and gut in cases where depression is not an issue. IBS patients with depression may be prescribed selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine (Prozac, Sarafem) or paroxetine (Paxil), as well as tricyclic antidepressants, such as nortriptyline (Pamelor), imipramine (Tofranil) or desipramine (Norpramin). These medications both treat depression and decrease the signals of pain travelling from the gut to the brain.

A lower dose of these drugs may be prescribed for IBS patients without depression, as tricyclic antidepressants can reduce pain and diarrhea, and SSRIs can reduce anxiety and constipation. Some people experience IBS relief with the use of anti-anxiety medication, like diazepam (Valium), but these medications are not widely used to treat IBS.

Probiotics and antibiotics

The normal bacteria living in the human gut is called the gut flora, and these microorganisms play a role in gut functions such as immunity, food digestion and nutrient production and absorption. An imbalance in these bacteria can affect gut function and overall wellness in many ways. Harmful bacteria can also cause infections.

Probiotics are supplements that introduce healthy, normal bacteria into the gut flora. More research is needed to prove their overall effectiveness, but some IBS sufferers do gain relief from the use of probiotic supplements. The most commonly studied probiotic for IBS treatments is Bifidobacterium infantis, and its effects are most promising in reducing gas and bloating.

Some IBS may be associated with an overgrowth or infection of harmful bacteria in the gut, and antibiotic medications that reduce bacteria are a possible treatment. The antibiotic Xifaxan (Rifaximin) is used to treat this kind of IBS, particularly improving stool consistency and decreasing pain. Some patients experience improvement in IBS symptoms in a single treatment with Xifaxan, while others require a longer course of treatment.

However, as individual gut flora makeup varies, and IBS can be triggered by both the overgrowth of harmful bacteria and the lack of beneficial bacteria, there is no consistent treatment of IBS using probiotics or antibiotics.

Other medications

Alosetron (Lotronex)
Alosetron is sometimes prescribed for women with IBS-D, as it slows the movement of waste through the bowel by relaxing the colon, as well as decreasing abdominal pain by blocking serotonin sensory transmitters from the gut to the brain. Due to rare but serious side effects, it is only prescribed by certain doctors and in extreme cases. It is not approved for use by men.

Lubiprostone (Amitiza)
Women suffering from IBS-C may be prescribed lubiprostone, which helps stool be passed by increasing fluid in the small intestines and stimulating peristalsis (muscle contractions of the gastrointestinal tract). It is only prescribed for women with severe constipation and IBS that has not responded to other treatments. This medication is not proven safe or effective for men with IBS-C, but may be prescribed for both men and women with chronic constipation but who do not have associated pain in the abdomen.

Eluxadoline (Viberzi)
Recently approved for IBS-D treatment in both men and women, eluxadoline improves consistency of bowel movements and relieves abdominal pain by decreasing bowel contractions. Eluxadoline is not appropriate for a person who has had their gallbladder removed.

Linaclotide (Linzess)
Adults with IBS-C may be prescribed Linaclotide (Linzess) (sold as Constella in Canada and Europe) for treatment of constipation, pain and bloating. It both blocks pain signals from the intestines and increases movement throughout the gastrointestinal (GI) tract.

Irritable bowel syndrome FAQs

Is it IBS, IBD, Crohn’s disease or ulcerative colitis?

IBS is often confused with IBD, a collection of inflammatory diseases including Crohn’s disease and ulcerative colitis. While symptoms such as diarrhea, constipation, gas and abdominal pain may be similar, IBD causes inflammatory damage to the intestines and colon that can be seen through visual inspection. As IBS does not cause damage like this, it is instead diagnosed through the appearance of symptoms.

People with IBS who pass bloody stool, lose weight or experience extreme cramping should go to a doctor to be evaluated for IBD or another serious condition. However, people with IBS are not more likely to develop IBD.

Can IBS cause cancer? Is IBS fatal?

IBS does not cause permanent damage or increase risk of colon or other cancers. IBS is not fatal.

Can IBS be cured?

As symptoms of IBS and their treatments vary from person to person, there is no single cure for IBS. However, individuals can manage their symptoms to minimize their effects on daily life and activities, sometimes ending their symptoms entirely.

Is medication necessary for IBS?

IBS can often be controlled through lifestyle and dietary changes, under advice from a doctor. Medications to control symptoms like cramping, diarrhea, constipation and gas, as well as stress and anxiety, may also be used.

Other names for irritable bowel syndrome

  • Spastic colon