DECODING THE LABEL

ONCE A DAY: Standard products degrade with sun exposure and rub off in around two hours. ‘Once a day’ products contain chemicals claimed to be more resistant, but even these should be reapplied if you’ve been sweating or swimming and towel dried yourself, says Clare O’Connor of Boots. Which? said a number of ‘once a day’ sunscreens wear off quickly — over the course of a day, an SPF30 could drop to SPF8.

WATERPROOF: This means the product keeps at least 50 per cent of its SPF protection after 40 minutes in water. So an SPF20 cream would have proved it’s at least SPF 10 after 40 minutes, which is why you still need to reapply after swimming.

SAND AND SWEAT-RESISTANT: These supposedly won’t be so easily removed by these factors. However, creams cannot be entirely resistant, so if you need this protection, you’d be better off using a UV protective top, says dermatologist Dr Justine Hextall.

SAFE FOR BABIES: These have been specially formulated, but everything should theoretically be safe for babies, says dermatologist Dr Anton Alexandroff. Physical sunscreens may be marginally better, as they’re less likely to cause allergic contact dermatitis, he says.

HYPOALLERGENIC: This usually means the product doesn’t contain known allergens. But there is no standard for what ‘hypoallergenic’ means, says Dr Hextall. Many studies suggest hypoallergenic products can still contain allergens.

APPLY TO WET SKIN: This is a new selling point. It contains chemicals that allow water on the skin to be absorbed into the product rather than diluting it. But Dr Hextall questions whether wet skin will reduce the potency of UV-protecting chemicals, or if these products will evaporate more quickly on wet skin.