The SPF index is a measure of sun protection. For example, if the skin usually starts to turn red after 20 minutes of sun exposure, then using sunscreen with an SPF of 15 will prevent redness 15 times more than the skin's natural defense.

2. It is recommended to reapply sunscreen regularly, as we may sweat or get wet. As a general rule, the lighter the skin color, the higher the SPF index needed.