Diarrhoea is a common problem experienced by most people at some point in their lives. There are many causes including infections, medications, foods and stress. Eating habits may also be a factor.

Viral and Bacterial Infections

Diarrhoea can be caused by several viral and bacterial infections. Common viral infections that cause diarrhoea include rotavirus (especially in children), norovirus and others. Bacterial infections that cause diarrhea are typically from contaminated food or water and include salmonella and E. coli. The most common cause of traveller’s diarrhoea is a bacterial infection.

Viral gastroenteritis is a common problem in the western world. The causes include contaminated water and food, contact with an infected person, unwashed hands or dirty utensils. Along with diarrhoea, the symptoms are abdominal pain, nausea, vomiting, sweating and fever.


Many medications, particularly antibiotics, may have diarrhoea as a side effect. Antibiotics fight off both bad and good bacteria in your body, so sometimes the balance in your gastrointestinal tract can be disturbed. Some blood pressure medications and the magnesium found in some antacids can also trigger diarrhoea. Always remember when taking prescription medications to talk to your doctor about any possible side effects.

Food Intolerance

Common causes of diarrhoea include lactose and gluten intolerance. Lactose intolerance occurs in people who lack the enzymes to break down lactose, which is a sugar found in milk and other dairy products. Gluten is a protein found in many types of grain, including wheat, barley, oats, and rye. Sometimes the immune system attacks gluten as if it were a germ. This results in inflammation of the intestine and leads to abdominal bloating, pain, diarrhoea, and gas. This condition is known as coeliac disease.

Stress, Anxiety and Other Causes

Stress and anxiety can play a role in causing diarrhoea. Artificial sweeteners containing sorbitol found in chewing gum and sugar-free products may cause it. Consuming too much caffeine or alcohol area may also be a cause as both may stimulate the intestines to make waste move too quickly through your body. It is thought that the hormonal changes associated with premenstrual syndrome may also be a cause. Other possible causes are appendicitis and intestine damage after radiotherapy.


Diarrhoea can be treated with medications from the pharmacy. Treatments containing loperamide are very effective and can be used early on to prevent the problem from getting worse. These treatments are particularly effective for treating diarrhoea in people with irritable bowel and loperamide should be the first choice in people with Irritable Bowel Syndrome (IBS), according to international guidelines.*

However, it is important to seek medical advice if symptoms are getting worse, the diarrhoea lasts for more than two days or you have abdominal swelling or bulging. These may be signs of a more serious condition.

Chronic or recurring diarrhoea may be a sign that you have an underlying condition such as IBS, ulcerative colitis or Crohn’s disease so it is important to see your doctor when this occurs.

After a bout of diarrhoea, your system needs a chance to recover. Rehydration can be achieved by drinking plenty of clear liquids. Oral rehydration solutions that contain electrolytes are also useful.

For a few days, it is preferable to avoid high sugar foods or those rich in fibre. Caffeine, alcohol, milk, fruit, green vegetables and spicy foods are best avoided also.

* Diagnosis and management of irritable bowel syndrome in primary care. NICE UK (National Institute for Health and Clinical Excellence 2008).