Probiotics are live bacteria and yeasts promoted as having various health benefits. They’re usually added to yoghurts or taken as food supplements, and are often described as ‘good’ or ‘friendly’ bacteria.

Probiotics are thought to help restore the natural balance of bacteria in your gut (including your stomach and intestines) when it’s been disrupted by an illness or treatment.

Probiotics may be helpful in some cases, but there’s little evidence to support many health claims made about them. For example, there’s no evidence to suggest that probiotics can help treat eczema.

However, it does seem that for most people probiotics appear to be safe. If you wish to try them – and you have a healthy immune system – they shouldn’t cause any unpleasant side effects.

Issues to be aware of

If you’re considering trying probiotics, there are a few issues you need to be aware of.

Probiotics are generally classed as food rather than medicine, which means they don’t undergo the rigorous testing medicines do.

Because of the way probiotics are regulated, we can’t always be sure that:

  • the product actually contains the bacteria stated on the food label
  • the product contains enough bacteria to have an effect
  • the bacteria are able to survive long enough to reach your gut

There are many different types of probiotics that may have different effects on the body, and little is known about which types are best.

Don’t assume the beneficial effects seen with one type are the same as other similar types or will be repeated if used for another purpose.

And there’s likely to be a huge difference between the pharmaceutical-grade probiotics that show promise in clinical trials and the yoghurts and supplements sold in shops.

When might they work?

Preventing antibiotic-associated diarrhoea (AAD)

There’s fairly good evidence that taking high doses of some probiotics (Lactobacillus rhamnosus or Saccharomyces boulardii) while taking antibiotics can help prevent children getting AAD.

Without probiotics, antibiotics can sometimes wipe out the protective gut bacteria, resulting in diarrhoea

Probiotics given with antibiotics may also reduce the risk of developing a Clostridium difficile (C. difficile) infection

C. difficile are potentially dangerous bacteria that can cause diarrhoea and life-threatening complications. They can infect the gut if the balance of gut bacteria is disturbed by antibiotics.

Probiotics are thought to directly kill or inhibit the growth of harmful bacteria, stopping them producing toxic substances that can make you ill.

Helping infectious diarrhoea

There’s some evidence that probiotics can shorten an episode of diarrhoea caused by a stomach bug by about a day.

But the evidence isn’t yet strong enough to make any treatment recommendations. Read our analysis of research into diarrhoea caused by a stomach bug.

Protecting premature babies

Some babies born prematurely are at risk of a serious condition called necrotising enterocolitis (NEC). This is when tissues in the baby’s gut become inflamed and start to die.

There’s some good evidence that probiotics may reduce the likelihood of premature babies developing NEC, although there are still some uncertainties, and routine use of probiotics in premature babies isn’t currently recommended.

Helping IBS

Probiotics may help reduce bloating and flatulence in some people with IBS

This is supported by a research published in 2010, although we don’t yet know the extent of the benefits or the most effective type of probiotic.

Probiotics won’t work for everyone with IBS, but if you want to try them, the National Institute for Health and Care Excellence (NICE) suggests taking them for at least 4 weeks, at a dose recommended by the manufacturer, to see if they help. 

Read the NICE guidelines for managing IBS in adults.

Helping lactose intolerance

Lactose intolerance is a common digestive problem in which the body is unable to digest lactose, a type of sugar mainly found in milk and dairy products.

Some studies have found that certain probiotics, such as Lactobacillus acidophilus, may help reduce the symptoms of lactose intolerance, which include stomach cramps, flatulence and diarrhoea.

Research into this is ongoing. In the meantime, if you’re lactose intolerant, you may wish to try probiotic preparations (not yoghurts) of Lactobacillus acidophilus to see if they help.

Helping pouchitis

Some people with ulcerative colitis need to have part of their bowel removed and a loop of bowel constructed in its place.

This loop, or pouch, can sometimes become inflamed, leading to diarrhoea and other problems. This is known as pouchitis.

Some studies have shown that certain probiotic mixes available on prescription can help treat pouchitis.

Unsupported claims

Probiotics don’t seem to help babies with colic

It’s been suggested that probiotics may be a useful treatment for babies with colic, but there’s little evidence to suggest they’re effective.

A 2013 study concluded that certain probiotics may help crying infants with colic who are exclusively breastfed.

But generally, it found insufficient evidence that probiotics can help manage colic effectively or prevent infants crying.

Since then, a small but well-conducted study found these probiotics had no effect on infant colic in either breastfed or bottle-fed babies. 

Read our analysis of this research.

Do probiotics boost the immune system?

Adverts for probiotic yoghurts used to claim they could “boost your immune system”, but these claims were ruled unproven by The European Food Safety Authority and can no longer be made.

There’s a lack of evidence that probiotics benefit the immune system, and research found probiotic supplements had no effect on antibody levels, days of fever and number of infections in healthy children.

There’s no reason why you should need to “rebalance” your gut bacteria if you’re already perfectly healthy, despite the claims made by some marketing material. 

Probiotics can’t be recommended for vaginal conditions

There have been suggestions that probiotics can help in the treatment of bacterial vaginosis. But even when they’re taken with antibiotics, there’s currently no evidence probiotics have any extra benefits.

The results of research into probiotics for vaginal thrush have been inconsistent and it’s not possible to recommend them as a treatment.

Probiotics can’t be used for IBD

There’s a lack of evidence to make any conclusions about the effectiveness of probiotics for relieving symptoms of Crohn’s disease or ulcerative colitis.

Probiotics aren’t supported for eczema

Some studies have suggested that giving probiotics to young children may reduce their risk of developing eczema, but the evidence isn’t very strong.

There’s no evidence to support claims that probiotics can help treat symptoms of eczema.

A 2008 review found probiotics don’t reduce eczema symptoms, such as itching, and they don’t change the severity of a person’s eczema.