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Does mouthwash go bad?

The question, “How long does mouthwash last before it expires?” is a bit like, “How long is a piece of string?”

Basically, all mouthwashes are different. Some contain alcohol, preservatives or antimicrobials.  Others don’t. This affects how long the product will last and continue to work.

But the quick answer is, yes. All mouthwashes expire eventually.

This article looks at:

  • How long mouthwash generally lasts before it expires
  • The impact of different ingredients on shelf-life
  • What happens if you use old mouthwash
  • Summary

How long does a bottle of mouthwash last?

The general rule of thumb is that mouthwash lasts two years from date of manufacture.  Some may last longer, depending on their ingredients (we discuss this below).

If a mouthwash has an expiration date this is a good sign. It tells you the manufacturer has invested time and money in testing to find out how long it will remain safe and effective for.

A mouthwash without an expiration date is not a sign that it won’t expire. It’s a sign that the makers haven’t tested how long the ingredients remain effective for before they degrade!  Use a permanent marker to write the date of purchase on the bottle and keep an eye on the contents. Check for signs of colour or texture change which show the mix is breaking down.

Where an expiration date is displayed, you should observe it and throw away the product when that date is reached.

We discuss the possible consequences of using mouthwash after its expiration date below. In most cases it is unlikely to harm you, but neither is it likely to be positively impacting on your oral health!

The majority of mouthwashes contain alcohol, antimicrobials or preservatives and these affect how long those products remain active and effective.

Alcohol

Most alcohol based mouthwashes contain ethanol which kills germs and bacteria. This not only helps to reduce plaque and gingivitis but also helps to preserve the product.

In addition, ethanol works to to dissolve and disperse essential oils like thymol or menthol which break down and prevent plaque.

Generally speaking, alcohol-based mouthwashes tend to remain effective for longer, sometimes up to three years after their manufacture.

But even mouthwashes containing alcohol won’t last forever. Light, temperature, air and interaction with other ingredients will eventually trigger processes that affect taste and efficacy.

Antimicrobials

Mouthwashes may contain antimicrobials as well as, or instead of alcohol. These help to preserve the product as well as helping to reduce and prevent plaque and gingivitis.

But mouthwashes also contain a high water content. So  over time, antimicrobial ingredients will begin to dissolve and break down. As they lose their effectiveness the chances for bacterial growth increases. The mouthwash will become compromised and needs to be thrown away.

One of the main antimicrobial ingredients in mouthwash is chlorhexidine. There are disputed claims that when chlorhexidine degrades it can become harmful, so even though it has an unopened shelf life of around 5 years, it is important to closely observe the expiry date and dispose of the product when it is reached.

Preservatives – Parabens

Parabens are the most common type of preservative used in mouthwashes.  They help to prevent the growth of mould or bacteria and to keep a mixture stable.  If a mouthwash contains parabens it may well last years beyond the expiration date.

However, research in 2004 showed that parabens can enter your body through the skin.  Once in your system they may cause hormonal changes that have been linked to cancer.  For this reason you may want to avoid mouthwashes containing them.

Natural mouthwashes

Concerns over the use of artificial chemicals have made natural mouthwashes increasingly popular.

If the product is purely natural then it will contain no preservatives.

You should stick to the expiry dates on purely natural mouthwashes. If there is no expiry date, mark the bottle with the date of purchase. Then watch for changes in appearance which may show the mix is breaking down. This include changes of colour, general appearance, texture or smell.

What Happens if You Use Out of Date Mouthwash?

Out of date mouthwash is unlikely to do anything to benefit your oral health. The ingredients will have degraded so are unlikely to protect you from gum disease, plaque build up, or bad breath!   

There is a small risk that out of date mouthwash could be harmful. If there is no alcohol in the wash the chemical mix may have broken down making bacteria build up within the wash more likely. In this case you will be adding to the bacteria build up in your mouth, when the whole point of mouthwash is to reduce it!

So it doesn’t make sense to use expired mouthwash. It will either not help you, or possibly make oral health problems worse. And you certainly should not use it if the colour or texture changes, or it starts to cloud. This is a definite sign that the product has degraded.

Summary

  1. All mouthwashes expire eventually, whether or not they have an expiration date.
  2. An expiration date is a good sign, it shows testing has taken place to work out how long the product is safe and effective for. So you should stick to it.
  3. If the product does not have an expiration date, it will still expire. Mark the bottle with the purchase date and keep an eye for changes in appearance, smell or texture.
  4. Always discard mouthwash that has begun to look, smell, taste or smell different. This is a sign the mix is breaking down.
  5. Alcohol based mouthwashes, or mouthwashes containing parabens, may last beyond their expiration date but see point 4.
  6. Antimicrobial ingredients are likely to break down in the high water content of a mouthwash – their expiry dates should definitely be observed.
  7. Using out of date mouthwash is unlikely to help oral health problems, and may contribute to them through build up of bacteria.

If you are really concerned about oral health, why take chances?  Go for a new bottle of mouthwash as soon as your old one is out of date!

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