Amazon's 'backed by science' £20 teeth whitening solution that promises two shades whiter - or you get money back

Amazon customers are raving about a teeth whitening product that they claim shows significant results from the first day. Hey Smile's Teeth Whitening Strips are a best seller from the brand and they're so confident in its whitening ability that if your teeth aren't two shades brighter they'll give you a full refund.

The strips are vegan friendly and cruelty free and they use industry-leading PAP whitening formula, which has been backed by scientific research against hydrogen peroxide, and is designed to make your teeth whiter, brighter and stronger. The formula promises to not lead to any tooth sensitivity or gum irritation which is often a concern when having teeth whitened.

Each box comes with 14 sachets of strips, which each sachet having enough inside to treat both top and bottom teeth. They're best applied to dry teeth that have recently been brushed, after 30 minutes they should be brighter and any leftover residue can be brushed off.

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Away from the brand's website, the Hey Smile teeth whitening strips are also available on Amazon. Here they are the same price of £19.99 for 14 sessions, but you won't get the same money back guarantee that you'll get by ordering directly through the Hey Smile website.

With an average rating of 4.9 out of 5 it's clearly popular. One shopper wrote: "Stains never appear since using this. My teeth are definitely whiter. My confidence in smiling has improved. Even my dentist was impressed."

A second penned: "I am 55 and this is my first time using teeth