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25 Sep 2020

What's in mouthwash and do you really need it?

Find out the truth behind mouthwash claims, what's in the bottle, and how to use it properly

Mouthwash is one more weapon in the fight against poor oral health, but is it essential, and what are you actually putting in your mouth when you rinse and spit?

The UK mouthwash industry is worth £158m a year*, so plenty of you are keen on that minty-fresh feeling.

But mouthwash has been subject to health scares in the past, and there's debate around whether or not it's actually necessary for optimum oral health.

We've delved into the science behind the bottle, with the help of Professor Damien Walmsley, scientific advisor to the British Dental Association, to demystify some of the key ingredients, common questions, and what to look out for when you buy.

The key points: mouthwash can be a useful extra step in your oral care routine if used correctly, but watch out for overblown claims, and there are some ingredients that can stain your teeth.

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What's in your mouthwash?

We've broken down the typical ingredients you'll find, what they do and anything you need to be aware of, using Listerine Total Care Mouthwash as an example.

Active ingredients

Active ingredients work to address the core concern the product is meant to target.

In the case of mouthwash, the active ingredients help to tackle gingivitis (gum disease), plaque, bad breath and tooth decay.

Sodium fluoride

The tooth-friendly benefits of fluoride are well documented. It's the key ingredient for helping to remineralise and protect teeth against cavities.

Mouthwash, such as Listerine's Total Care, typically has a relatively small amount compared with toothpaste - in this case, 220ppm (parts per million). Fluoride toothpaste typically contains 1,350-1,500ppm fluoride.

So, while mouthwash has its uses, toothpaste is essential for a good dose of fluoride.

Professor Walmsley warns that, while it may seem like the natural thing to do, it's important not to use mouthwash just after brushing. This is because you end up washing away the (higher-strength) fluoride from your toothpaste. Instead, leave at least an hour in between the two, or use mouthwash at a different time of day.

Essential oils

Essential oils, such as eucalyptol, thymol, menthol and methyl salicylate (found in Listerine Total Care), serve two purposes - giving a zingy fresh taste and fighting bacteria.

In combination, these essential oils have been shown in scientific studies to have properties that help prevent bacterial and fungal growth in the mouth.

'There's some evidence that this concoction of essential oils is able to disrupt the bacterial coat, helping to prevent tooth decay and gum disease,' says Professor Walmsley.

Zinc chloride

'Zinc chloride helps to help reduce halitosis (bad breath), which is one of the main reasons people use mouthwash,' says Professor Walmsley.

Research has shown that zinc ions bind to hydrogen sulphite, a cause of bad breath, as well as suppressing the growth of oral bacteria.

Other mouthwash ingredients and what they do

Alcohol (ethanol) - helps disperse ingredients

Alcohol acts as a carrier for ingredients like essential oils in mouthwash, enabling them to disperse bacterial communities (biofilms) that cluster together to form plaque and lead to tooth decay.

Professor Walmsley says: 'There was a scare a while back because of the link between alcohol and oral cancer, but there isn't sufficient evidence that the use of mouthwashes containing alcohol can influence this.'

However, people who get a dry mouth may find that mouthwash with alcohol worsens the condition.

If you would rather steer clear of alcohol for reasons such as health, culture or lifestyle, alcohol-free mouthwashes are available.

Sweeteners - for taste

Sweeteners, such as sodium saccharin, sucralose and sorbitol, help 'to make mouthwash more palatable', says Professor Walmsley.

Sodium saccharin is a calorie-free artificial sweetener, whereas sorbitol and sucralose are sweet-tasting sugar alcohols (polyols).

Unlike traditional glucose-based sugars, they don't cause decay because they aren't broken down by oral bacteria in the mouth - a process which releases acids that can lead to cavities and the erosion of enamel.


Preservatives, such as benzoic acid and sodium benzoate, increase the shelf life of a mouthwash.

Surfactants - to help ingredients mix

Surfactants help to dissolve oily ingredients (such as essential oils) in water. Listerine Total Care uses Poloxymer 407 for this function.

Professor Walmsley says: 'It helps to break the water tension so that the product has more wetability, enabling it to reach all areas of the mouth.'

Other common surfactants include sodium lauryl sulphate, though some studies have shown this can cause irritation.

Colourings - to make it look appealing

These serve no real purpose but to make the product look appealing and stand out on the shelf.

While many mouthwashes opt for bright blue or green to denote minty freshness, Listerine's Total Care has a distinctive purple tinge, created by synthetic dyes CI 16305 (Allura Red) and CI 42090 (Blue 1).

While mostly benign, Professor Walmsley warns: 'Some people have a hyperactivity reaction to colourings,so if this is you it's worth checking the ingredients list.' Some mouthwashes are colour-free.

Mouthwash for whitening and sensitive teeth

Some mouthwashes claim to go the extra mile, with ingredients to help whiten teeth or reduce sensitivity.

While we suggest you take the whitening claims with a pinch of salt, mouthwashes with ingredients to reduce sensitivity could be a helpful extra for those with unpleasant tingles.

EU regulations mean that whitening products in the UK can only contain a maximum of 0.1% of the typical whitening ingredient, hydrogen peroxide.

But this is too low to have any real effect. Some products may have a blue tinge to provide an optical brightening effect, but at most this will be temporary.

What about charcoal mouthwash?

The demand for natural dental products is on the rise, and charcoal is an increasingly fashionable mouthwash ingredient that has claimed whitening and stain-removing properties.

However, research shows there's no evidence to suggest that charcoal mouthwashes are beneficial to oral health.

In fact, they may even cause enamel damage due to the abrasiveness of charcoal particles.

Professor Walmsley says it straight: 'There's nothing to say charcoal mouthwashes are useful.'

Active ingredients for sensitive teeth

Ingredients such as calcium oxalate and hydroxyapatite work to remineralise teeth and block dentine tubules, which are channels in the underlying dentine area of the tooth that lead to the inner tooth pulp and can cause sensitivity if exposed.

Potassium nitrate works by calming the nerves in the teeth. Both have been shown in studies to help with sensitivity.

In fact, a 2019 study showed that twice-daily use of a mouthwash containing potassium salts provided significant improvements in tooth hypersensitivity compared with fluoride toothpaste alone.

If you don't want to use a mouthwash, look out for these ingredients in a toothpaste instead.

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Expert verdict

Mouthwash 'nice to have', but not essential

Professor Walmsley says: 'Some people want their mouthwash to do everything but it should always be seen as an adjunct rather than essential.'

He stresses that it's more important to brush regularly with a fluoride toothpaste (spit out, don't rinse, to ensure the fluoride coats your teeth) and to floss.

This should be sufficient to eliminate the bacteria that causes bad breath. If you have a persistent problem, it's worth consulting your dentist.

Watch out for this one mouthwash ingredient that can stain teeth

Some mouthwashes can actually end up staining your teeth.

Professor Walmsley says: 'Chlorhexidine is a relatively common mouthwash ingredient. It's extremely effective at killing bacteria but it also tends to stain teeth, and this staining is hard to remove.'

This ingredient is usually found in high-strength mouthwashes for those with more problematic oral health, such as Corsodyl Gum Treatment, and shouldn't be used long term.

Other common mouthwash queries:

Can children use mouthwash?

Mouthwash shouldn't be used by young children and they certainly should never be given mouthwash containing alcohol.

Some products state they are suitable for 6+ years, although Public Health England (PHE) recommends that children from the age of eight and young adults can use a mouthwash if they have active caries (decay that has worsened over time).

But it's probably more trouble than it's worth. It's harder to prevent them swallowing the mouthwash, and it's most important to work on instilling the habit of regular brushing, visits to the dentist at least once a year and a healthy diet.

Some mouthwash ingredients may have an effect on young children, if swallowed. Sodium benzoate may increase hyperactive behaviour, and sorbitol can have a laxative effect.

So it's important that, if used, mouthwash use is supervised to prevent swallowing, and look for a child-friendly formulation.

Is 'oil pulling' a substitute for mouthwash?

Oil pulling is a process of swilling oil round your mouth, like mouthwash, in a bid to remove bacteria and improve oral health.

It's an alternative medical practice that has its roots in Ayurvedic medicine.

However, the American Dental Association says there's insufficient research to support it for oral hygiene.

In fact, a study has linked oil pulling with recurrent lipoid pneumonia - a chemical lung disease caused by breathing in small amounts of oil.

*Oral Care: Top Products 2019, The Grocer and Nielsen.