Imagine you’re attending a summer wedding or sports day, or just planning a trip to the park or beer garden. You have slathered on a generous layer of SPF and feel smugly well prepped against sunburn and premature ageing.
What you may not realise is that you’re good only for the next two hours. Depending on which study you believe – from the US’s Johns Hopkins medical school to the NHS – sunscreen should be reapplied every 120-180 minutes if it is to continue to be effective. As with much medical advice (your five-a-day fruit and vegetables, for one), this rule is scientifically sound – but is it remotely likely that people are going follow it to the letter?
