How are Sun Protection Factors (SPF) for sun-screens calculated?
In order for a sun-screen to claim a given Sun Protection Factor it must contain one or more filtering agents that are approved under European legislation. This legislation not only sets out which ingredients may be used but also gives the percentages of each ingredient that the finished product must contain in order to achieve and claim a given level of protection. This ensures that sun-screen products made by different manufacturers using different ingredients can be compared on a like-for-like basis.
