What is diarrhoea?

Diarrhoea is a common condition when a person’s bowel motions become loose and watery, and the urge of frequency to empty your bowels increases to more than three times in any 24-hour period.

This usually occurs due to a disruption in the lining of the intestines, where fluids are unable to be absorbed normally, or more fluid is being drawn out into the intestines.

Most causes of diarrhoea will resolve itself within a day or two, with symptoms completely resolving in less than two weeks without treatment. However, more severe cases with underlying issues may become quite debilitating and will require further investigation and treatment.

What are the symptoms associated with diarrhoea?

In addition to the increased urgency and loose nature of bowel motions, the following are also usually associated with diarrhoea:

  • Abdominal cramping

  • Nausea and/or vomiting

  • Fever

  • Headache

  • Bloating

  • Loss of appetite

  • Lack of energy and general feeling of weakness

As diarrhoea effectively drains the body of fluids, dehydration can set in quickly, especially in young children. Signs of dehydration may include:

  • Dry mouth or tongue

  • Decreased urination, or dark urine when passed

  • Increased thirst

  • Sunken eyes

  • Loss of skin elasticity

  • Light-headed or irritable

Causes of diarrhoea

The intestinal lining plays a major part in the absorption of nutrients from food, medications, and most importantly water. When there is inflammation in the intestinal wall, this offsets these absorption processes, leading to watery, loose stools.


Viruses are the most common cause of diarrhoea, especially in children and the elderly, where the immune systems are not fully developed or are compromised. Amongst the known viruses that cause diarrhoea, rotavirus and norovirus are the most well-known. Rotavirus infects mainly children, as adults have generally developed an immunity to it. Norovirus is known to infect those who are near each other for extended periods of time, such as on cruise ships, in nursing homes or in hospitals.


There are a number of bacteria which can cause diarrhoea, most of which are transmitted by ingesting contaminated foods. Some of the more familiar bacteria known to cause infections include the E.coli, Salmonella, Shigella and Campylobacter species. Raw foods or foods not cooked properly are also at risk of carrying these bacteria.


Whilst not as common as viruses or bacteria, parasites such as Giardia found in contaminated water sources are also known to cause diarrhoea.


A number of medications can also cause diarrhoea-like symptoms due to its intended action or as a side-effect. Antibiotics, as an example, can disrupt the normal good bacteria that exist in the intestines, and therefore lead to an impairment in its function.

Speak to one of our pharmacists to discuss whether one of the medications that you are currently taking could be the cause of your symptoms.

Existing medical conditions

Inflammatory bowel diseases such as Crohn’s disease and ulcerative colitis are the main medical conditions which can cause diarrhoea, but inversely can also cause constipation. Irritable bowel syndrome (IBS) is another such condition.

Food intolerances can also increase the symptoms associated with diarrhoea. This can include conditions such as lactose intolerance, or from the excess consumption of different types of sweeteners.

Management and treatment of diarrhoea

Depending on what the cause of the diarrhoea is, there are different approaches to managing the symptoms.

The first step of managing diarrhoea caused by infection is to prevent or reduce the risk of any further transmission. Washing hands with soap and water thoroughly will reduce the likelihood of spreading the virus or bacteria.

Most cases of diarrhoea are self-limiting and will get better by itself as time passes. It is important to maintain adequate hydration during this time, and to avoid any triggers that may cause the diarrhoea to become worse.

  • Drink plenty of clear fluids such as water, broths or rehydration fluids

  • Avoid dairy foods

  • Avoid fatty, greasy and spicy foods

  • Avoid alcohol

  • Avoid caffeine

  • Avoid soft drinks, energy drinks and sports drinks

  • Eat bland foods (such as plain biscuits, rice, toast) when hungry

As mentioned above, rehydration fluids are recommended to help the body take up as much fluid as possible as it passes through the intestines. Products such as Gastrolyte and Hydralyte are specifically formulated to ensure this occurs. Dilute fruit juice or soft drinks, energy drinks and sports drink formulations contain a lot of sugars and sweeteners (and often caffeine), which will make the diarrhoea worse.

There are anti-diarrhoea medications which are available over-the-counter which can help slow down the bowel motions and help with stomach pains and cramping. Although useful in the short term, whenever possible, it is recommended to allow the diarrhoea to run its course and supplement with oral rehydration fluids especially if the cause is a bacteria or virus.

Speak to our pharmacists to discuss which products are available and would be suitable for you.

When to see your doctor

There are times when the body is unable to completely deal with the diarrhoea on its own or there are underlying problems, in which case it is advisable to seek an advice from a medical practitioner.

Please see your doctor if:

  • A child or elderly person has severe diarrhoea

  • The diarrhoea lasts for more than 5 days

  • There is bright red blood in the bowel motions, or they are dark and tarry

  • Mucus or high amounts of fatty waste is present in the bowel motion

  • There are foul smelling odours in the bowel motion that is unable to be flushed away

  • You are vomiting repeatedly

  • You have a high temperature, skin rash, severe abdominal pain or cramps

  • The diarrhoea was from travelling overseas

  • There is associated weight loss

  • There are pre-existing conditions such as diabetes, heart failure or kidney failure

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