Avoid sun exposure between 11am - 3pm. Seek shade and always protect children with a hat, loose clothing and high SPF protection. Physical/mineral products reflect visible light as well as UV, which can make the formulations opaque and leave a white residue on the skin. Some formulations use nanoparticles of titanium dioxide and zinc oxide – the minerals responsible for the residue. Nanoparticles are smaller, and as they scatter visible light – rather than reflect it – the sun creams are transparent. How to use sun cream We agree that the claim “Once a day” can be anticipated in a wrong way by the consumer, and it is one of the reasons why we changed our durability communication from “Once a day” to “Up to 10 hours”. 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. 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

There’s a long list of ingredients that are used as chemical absorbers, so it’s easiest to simply look for products that are labelled ‘sensitive’ rather than search for specific ingredients. SPF make-up: does it really offer protection from the sun? Even with our test subjects just sitting on a chair in a T-shirt, we saw substantial reductions in the level of sun protection, so we don't think you can rely on once-a-day sun cream to keep you protected all day. 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. 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. If you're using sun cream at the beach, apply plenty before swimming, and again when you leave the water. Reef-safe sun creamsWhen choosing sun cream for your child, look for a short ingredients list and the terms 'fragrance free' and 'hypoallergenic'. The WHO recommends 35ml of sun cream (seven teaspoons' worth) to cover an adult, so use around a quarter to a half of this depending on the size of your child. 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.' Sun cream provides protection from sunlight using UV filters. These are classified into two types: chemical and physical – also known as mineral sun cream.

Do not exceed exposure to the sun for longer than your skin type allows, taking into account the strength of the sun. 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.' Boots Professor Brian Diffey adds that sun creams generally offer ‘very good’ water resistance these days (though be aware water resistance claims also come with caveats, and the products we tested didn't hold up well to real-life conditions in our 2016 investigation), which is good if you're planning on spending time in the pool or in the sea. But over the course of the day swimming will wash away some of the protection.

Find out what you need to know about 'once a day' sun creams, water-resistant sun creams, sensitive sun screen and the best kids' sun cream too. Calypso Once A Day may cause staining on certain fabrics and surfaces. Always cover seats and cushions. May discolour nail products. 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. Casting incorrect assertions in this manner is misleading and confusing to customers and we are disappointed that Which? has chosen to do this.' Calypso

Apply to all exposed areas especially those that are prone to sun radiation e.g. face, nose, receding hairline, shoulders and feet. Some people worry that using sun cream might prevent them from getting enough vitamin D, but this isn’t the case unless you really overdo it. What's more, even if you follow all the rules, it's possible you won't get as much as protection as you expect. The regular reapplication advocated by most sunscreens protects us against this,’ he says. To apply sun cream properly you should: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). 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 For reasons of hygiene and safety, personal grooming products, cosmetics or items of intimate clothing cannot be returned. Cover up – wear sunglasses to protect your eyes and grab a hat if you need to keep your face out of the sun. You might also want to wear a T-shirt, which can help to cover up typically over-exposed areas such as shoulders.

The British Association of Dermatologists (BAD) says frequent reapplication of sun cream is important, regardless of how long any product claims to give protection for.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.