We made multiple attempts to get in touch with Calypso, but the brand did not respond to any of our questions or send us a comment. Riemann

Avoid sun exposure between 11am - 3pm. Seek shade and always protect children with a hat, loose clothing and high SPF protection. So, if you are only applying your sunscreen once a day, you are at risk of spending hours in the sun with little or no protection to those areas of skin that may have been missed.' It's clear that there are plenty of conditions to fulfil to get the claimed protection from once-a-day products, which may be hard to achieve if you're on a day out in the sun. People can still use these types of sunscreens, but you should treat them like any other sunscreen, and reapply regularly,' he said.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

Calypso Once A Day may cause staining on certain fabrics and surfaces. Always cover seats and cushions. May discolour nail products. 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. 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. 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. Reapply sunscreen after swimming, sweating heavily, towel drying, or rubbing your skin in a way that might cause the cream to rub off.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.' 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. Apply evenly and generously, smooth in gently. We recommend a minimum quantity of 35ml for all over body protection. 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.

Yes, you can - but you’ll also need to reapply frequently, just like you would if you were on the beach staying dry, and immediately after towel drying. Important: Read the instructions carefully before use. Apply to clean dry skin, preferably after a shower. Apply evenly and generously 15 minutes before exposure to the sun, which will allow the product to bind with the skin and form a protective film against UVA/UVB rays. When used correctly, one application is sufficient for all day protection. Over the course of a day, he added, 'swimming, drying, sweating, getting dressed and undressed' can cause sun cream to be wiped or washed away. A spokesperson added: 'As with all sunscreens, it is important to follow the instructions for application and use; and sunscreen should not be used to intentionally stay longer in the sun. Sunscreen is just one part of a sun safe regime.' BootsThe British Association of Dermatologists (BAD) says frequent reapplication of sun cream is important, regardless of how long any product claims to give protection for. 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. Don't just rely on sunscreen either: use clothing, hats, sunglasses to cover up, and seek shade, particularly when the sun is strongest, between 11am and 3pm - regardless of whether you are wearing sun cream. Apply a generous amount of sun cream - around one teaspoon per body part - at least 15 minutes before you go into the sun so it soaks in.