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”. 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

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. 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. 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. If you're using sun cream at the beach, apply plenty before swimming, and again when you leave the water. Reef-safe sun creamsFrom April to September, when the UV Index is generally higher. It takes 10 to 15 minutes of sun exposure each day for those with fair-to-olive skin to get enough vitamin D. Eat well, live better and stay healthy - sign up for our free monthly Food & Health newsletter for the latest insights delivered straight to your inbox 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.'

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). Apply to all exposed areas especially those that are prone to sun radiation e.g. face, nose, receding hairline, shoulders and feet.

Physical or mineral sun creams create a barrier on the skin that acts like a mirror, reflecting and scattering the UV light. We award Which? Best Buy status to products that we've independently reviewed that meet all our tough criteria: they must pass independent lab tests for UVA and UVB sun protection, and be easy and pleasant to apply. The industry guideline for water-resistant sun creams allows the SPF of a product to drop by 50% after a total of 40 minutes in water. Water-resistance testing also takes place in what is essentially a bath – using tap water. Always be aware of the strength of the sun. Never exceed sun exposure for longer than your skin allows. Remember - all skin types are different. 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.