What SPF actually means

SPF compares the ultraviolet exposure needed to produce sunburn on protected and unprotected skin under standardized testing. It primarily reflects UVB-related protection and is not a count of hours. Broad-spectrum labeling addresses protection against UVA as well.

In real life, thin application, rubbing, sweat and water can reduce protection. A higher number cannot compensate for missed areas or eliminate the need for reapplication.

For general outdoor care, AAD guidance recommends broad-spectrum SPF 30 or higher, adequate application before exposure and reapplication about every two hours and after swimming or sweating. Shade, hats and clothing remain important.