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.

There's some evidence that probiotics may be helpful in some cases, such as helping to ease some symptoms of irritable bowel syndrome (IBS).

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.

But for most people, probiotics appear to be safe. If you want to try them, and you have a healthy immune system, they shouldn't cause any unpleasant side effects.

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 go through 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.

You may find a particular type of probiotic helps with one problem. But this doesn't mean it'll help other problems, or that other types of probiotic will work just as well.

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.

If you have an existing health condition or a weakened immune system, you should talk to a doctor before taking any probiotic supplements.