Sun protection factor (SPF) is a measure of a sunscreen's ability to protect the skin from the harmful effects of ultraviolet (UV) radiation. Sunscreens with a higher SPF provide more protection than those with a lower SPF.
In general, sunscreens with an SPF of 30 or higher are considered effective at protecting the skin from the harmful effects of UV radiation. Sunscreens with an SPF of 60 or higher may provide slightly more protection than those protection than those with a lower SPF, but they are not necessarily any more harmful.
However, it is important to use sunscreens properly in order to get the maximum benefit from it. This includes applying it generously and evenly to all exposed skin, and reapplying it every two hours or immediately after swimming or sweating.