The pursuit of a sparkling smile is a popular one in today's Insta-perfect world. Attracted by promises of brighter, whiter teeth, consumers are buying a dazzling array of whitening powders, paints, gels, pens, strips and kits to use at home.
According to a recent Mintel report, 52% of people surveyed were using at-home teeth-whitening kits at least once a day.
They're usually much cheaper than dentist-administered professional whitening, but are home whitening kits really effective - and are they safe for your teeth?
We've looked into what they contain and what to watch out for, and found it's unlikely you'll get the results you desire at home.
As part of our research, we also uncovered international sellers posing as UK-based sites and selling illegal whitening products to UK consumers. We have reported them to Trading Standards.
The gold standard treatment for achieving whiter teeth involves using hydrogen peroxide at concentrations of up to 6%.
In the UK this can only be carried out by a dental professional - either a dentist, or a dental hygienist or therapist under the supervision of a dentist.
It is illegal for anyone other than a dental professional to carry out tooth whitening using this concentration of hydrogen peroxide, and they must be registered with the General Dental Council (GDC). Beauticians cannot carry out the procedure.
Professional bleaching usually involves:
Even when carried out by a professional, whitening can sometimes cause side effects such as temporary sensitivity, gum discomfort, white patches on the gumline or a sore throat for a few days. A good mouth tray fit and following the guidelines should help to minimise these issues though.
Over the counter home whitening kits are widely available in the UK, but can't contain more than 0.1% hydrogen peroxide under EU regulations. This is because of the risk of damaging or burning your gums or mouth if kits are used incorrectly.
The Oral Health Foundation (OHF) says that the concentration of hydrogen peroxide allowed in home kits is too low to have a noticeable effect on the underlying colour of your teeth, no matter what the manufacturer promises.
It's possible that the kit may include other stain removing ingredients which could help teeth look whiter, but you could probably achieve this equally well with a stain-removing or whitening toothpaste.
Bear in mind too that the colour shade charts provided in these kits - included so they can promise 'up to 10 shades lighter!' - are likely to be very different to the colour scales used by dentists, and their interpretation of a change of shade may be a smaller incremental change.
The addition of blue or UV light, included because it's claimed to speed up the whitening process, is also unlikely to make any difference to the end result - unlike the power or laser whitening that some dental professionals offer.
You should also treat any UV-light product with caution and protect your eyes and other exposed areas from the light.
Because of the extremely low levels of hydrogen peroxide allowed in home kits, some use other ingredients with claimed whitening potential such as sodium chlorite and phthalimidoperoxycaproic acid (PAP).
While it is possible that some of these chemical ingredients could lighten your teeth, a recent study published in the British Dental Journal found that they could also potentially damage tooth enamel, especially when the kits were used for longer than as directed.
However, more research is needed in this area as the study was fairly small scale and had certain limitations.
We've seen tips online and on social media that suggest painting hydrogen peroxide directly onto your teeth.
It's easy to get hold of 3% hydrogen peroxide legally - it can be used as a skin disinfectant or as a mouthwash, but should always be diluted with water.
Dr Nigel Carter, Chief Executive of the OHF says 'using undiluted peroxide directly on the teeth could lead to damage to your gums and this concentration of hydrogen peroxide shouldn't be ingested. There is also a danger of splashing the solution in your eyes and causing damage'.
The real risk comes when you buy kits from sellers that are either not based in the UK or who are selling illegal products.
Trading Standards told us it regularly comes across sellers trading non-compliant products online, and these can have serious consequences.
In 2016 a father and son were jailed for selling hydrogen peroxide kits containing 110 times the legal limit. One of their customers had to have hospital treatment for chemical burns.
We bought products from two sites that on first appearance seem to be UK-based retailers - www.ukteethwhitening.com and www.crestwhitening.co.uk.
Both sell Crest Whitening Strips that are available in the US but aren't approved for sale in the UK as they contain well over the legal limit of hydrogen peroxide here.
Procter & Gamble, which manufactures Crest whitening strips, does not authorise their sale in the UK because it knows they do not comply to the regulations.
We investigated, and found that one of the companies selling the product to UK consumers is based in Hong Kong and the other, Canada. Both are using UK fulfilment centres to get around regulations, as both products we ordered arrived within 48 hours of ordering.
The products came with no instructions and were unboxed. The Crest strips from www.crestwhitening.co.uk had no ingredients list. This presents further risk as you don't have the information to use them correctly and don't really know what you're getting.
We reported our findings to Trading Standards who confirmed that these products are non-compliant and are now investigating further action.
Neither retailer responded when we approached them for comment.
It may seem like lower-risk option when a product is legal elsewhere, but that isn't necessarily the case.
Richard Knight, Specialist Trading Standards Officer and expert in cosmetic product safety says: 'At the end of the day any home tooth whitening kit involves a concoction of chemicals which will all have a toxicological profile. Any formulation needs to be signed off with a UK or EU-based qualified safety assessor.
'An illegally imported or distributed product simply won't have gone through this process and won't be subject to recognised quality control and could therefore be harmful to a consumer, even if the ingredient list seems relatively benign.
'Additionally, if you do buy from someone not based in the UK or perhaps operating via a UK fulfilment centre, when you do have an issue, you are likely to find getting any redress, or indeed, just getting in contact at all, very challenging.'
Anyone suspected of providing illegal products should be reported to Trading Standards.
So what's the bottom line? It's possible that home whitening kits may give some results if you're looking to restore a whiter smile, but be wary of what you buy and who from, to avoid kits that contain unproven or potentially harmful ingredients. Always follow the instructions carefully too, and don't be tempted to overdo it.
You're likely to get better results from a professionally administered treatment though, so it's worth chatting to your dentist for advice if you have concerns about your smile, and giving a stain-removing toothpaste a try too. Check our for advice on effective stain-removing ingredients.