Teeth-whitening kits sold online have been found to contain illegally high levels of a bleaching chemical which can burn gums and cause tooth loss.
An investigation carried out by Which? found that the worst had 300 times the recommended amount of hydrogen peroxide, while a further 21 out of 36 kits tested also had illegal levels of the bleach.
The consumer group said it was concerned that social media users may be encouraging others to use products with dangerous levels of the chemical.
Sue Davies, Head of Consumer Protection Policy at Which?, said: “It’s worrying that our tests have revealed so many of these products sold on online marketplaces – and often hyped on social media – are breaking legal limits for hydrogen peroxide and putting the health of users at risk.
“It’s clear that self-regulation is not working, leaving people exposed to a flood of unsafe products online.”
Online marketplaces, including Amazon, eBay and AliExpress, have now removed the unsafe products from sale.
Over the legal limit
Teeth-whitening products sold for use at home can contain no more than 0.1 per cent hydrogen peroxide, while the legal limit for application by professional dentists is 6 per cent.
Of the products tested by Which?, a total of six kits contained more than 10 per cent hydrogen peroxide.
One bleaching gel kit contained 30.7 per cent hydrogen peroxide, from the Oral Orthodontic Materials store on AliExpress.
The company said it had “found the mistake, corrected it in time and that the product has been removed from sale”.
In response to the findings, AliExpress told the consumer group: “We take product safety very seriously and after being notified by Which? of its findings, we took prompt action and removed the third-party product listings identified to be in violation of our listing policy.
"We are a third-party marketplace and all merchants selling on AliExpress must comply with our platform rules and policies, as well as comply with all local laws and regulations.
“We will take action against sellers that are found to be in violation of our terms."
Advice for consumers
Consumers have been advised to be wary of whitening kits sold online as high levels of the bleaching chemical can cause lasting damage.
Dr Paul Woodhouse from the British Dental Association said: “Hydrogen peroxide is a seriously strong chemical and not to be messed with.
“Dentists are trained in its usage and they also know what whitening products are effective to use and safe for teeth and gums.
“If you destroy gum tissue, you are never going to get it back and you lose your teeth. If it penetrates the surface of your tooth, which is likely, it’s probably going to lead to the death of that tooth.”
Consumers who are looking to buy teeth-whitening kits online are advised to buy the product from a reputable high-street retailer, as the legal responsibilities to ensure products are safe for use are much stronger than on online marketplaces, according to Which?.
Melike Aytekin, Dentist at Vera Clinic reiteratated the importance of professional teeth whitening over home kits, adding: “Teeth whitening is a complex process, and buying a kit off the internet is asking for trouble.
"Primarily, it is impossible to know exactly what’s in the tooth whitening kits, and many contain illegal amounts of bleach. Once your teeth and gums are damaged, it’s likely they will never be the same again.
"High concentrations of carbamide peroxide or hydrogen peroxide teeth whitening gel, often in tooth whitening home kits, are not safe for areas of the mouth such as the cheeks, lips, tongue and gums. If the gel comes into contact with these soft tissues, it will result in chemical burns.
"Furthermore, research shows that the use of these strong chemicals on tooth enamel leads to a decrease in its microhardness. It can also cause a change in the mineral content of enamel, weakening it and making it more susceptible to cavities. If teeth whitening gel comes into contact with the nerve of a tooth through a cavity, this can cause permanent nerve damage, which leads to extensive dental treatment.
"This is the exact reason why professional teeth whitening is always safer; professional gels have minerals added to them which work to strengthen the enamel and counteract the effects of the chemicals.
"It’s always worth paying a bit more to protect your teeth and gums, as damaging them could cost you significantly more money, and hassle, in the long run.”