Professor Brian Diffey, of BAD, says: 'We recommend against relying on any sunscreen product for long periods without reapplication, whether advertised as an extended wear product, or not. This is because, she said, the length of protection can vary depending on a person's activities - including how much they sweat and whether they towel dry, for example.

The regular reapplication advocated by most sunscreens protects us against this,’ he says. To apply sun cream properly you should: And after that, he adds, re-apply at least every two hours - and immediately after swimming, sweating or towel drying. A spokesperson told us that all of its sun creams are designed for 'longevity' but that it found the use of the word 'durable' more 'appropriate' than once a day.In 2016 Which? put several once-a-day sunscreens to the test, investigating how long they lasted on volunteers in a controlled lab experiment, and found they didn't offer nearly as much protection as claimed. Mineral sunscreens fail Which? SPF and UVA tests - find out what happened when we put pricey mineral formulations to the test in our independent lab

Apply to all exposed areas especially those that are prone to sun radiation e.g. face, nose, receding hairline, shoulders and feet. I had difficulty getting hold of my usual day-long sun cream so took a chance on this. . As others have said, it’s a gel and not a cream, but it absorbs super fast and it’s easy to apply. 2 weeks in day-long sunshine over 30 degrees and I have a good tan and no sunburn. I also usually suffer from heat rash but not with this product. They were allowed to wear t-shirts and sit on a chair (we did this because if you lie on a sun lounger or towel, get sandy, or wear a t-shirt on holiday it’s possible your single-use sunscreen could be rubbed off over time). Nobody applies sunscreen perfectly uniformly to all exposed skin and it is inevitable that we will miss patches of skin.Apply evenly and generously, smooth in gently. We recommend a minimum quantity of 35ml for all over body protection. Great once-a-day sunscreen. It's a clear gel, very easy and smooth to apply, and doesn't leave a residue on your hands. No need to reapply!

A spokesperson said: 'Soltan Once products clearly state how they should be used and when to reapply. We are confident in the claims for the Soltan Once range and refute the suggestion that they are misleading. Once a Day SPF40 Sun Protection (150ml) is water resistant so only one application is needed for the whole day. The formula provides protection from the sun’s damaging rays and is specially enhanced and designed to protect children’s delicate skin. What's more, even if you follow all the rules, it's possible you won't get as much as protection as you expect. We asked Boots a series of questions about its Once sun cream range and asked it to respond to our concerns about 'once a day' claims. Professor Brian Diffey recommends applying sun cream like you would paint to a wall - you'd rarely just do one coat. Two coats of paint are almost always required for satisfactory coverage. In the same way two coats of sunscreen may be required for adequate protection,' he said.Use in the water - Claims to maintain 'intact' protection levels even after 4 x 20 minute sessions in the water. People can still use these types of sunscreens, but you should treat them like any other sunscreen, and reapply regularly,' he said. The use of the word durable, she added, aims to communicate its long lasting characteristics without 'promising [a] full day protection guarantee, with no need for reapplication.' Use in the water - up to 40 minutes of water exposure (up to one hour for the kids version, and up to three hours if you opt for Boots Soltan Kids Once 3hr Waterplay Spray) Since our 2016 investigation, the CTPA has advised brands to voluntarily stop making 'once a day' claims and move towards using the word 'durable' instead.