Her Health > Women's Health > You Don’t Need a PhD To Understand SPF

It seems simple enough. The higher the Sun Protection Factor (SPF) of your sunscreen, the longer you can stay safe in the sun. So why are so many people walking off the beach, SPF 40 in hand, sporting a fiery flush on their face?

SPF measures the amount of solar energy (or UV radiation) it takes to produce sunburn, and not the amount of time. What’s the difference? The sun is stronger at certain times of the day and at certain times during the year. You will burn faster at 1 p.m. than at 4 p.m. You will also burn faster if you are fairskinned, don’t apply enough sunscreen or neglect to reapply it during the day.

It is important to remember that SPF is a relative measurement of ultraviolet B (UVB) protection that is determined in a laboratory environment, not in natural sunlight. It provides a reasonable estimate of how long you can stay in the sun before getting sunburn, but it does not measure ultraviolet A (UVA) protection. UVA rays are those most responsible for skin cancer and skin aging.

Play it Safe:

Wear a sunscreen with an SPF 30 or above

Read the label: Make sure your sunscreen protects against both UVA and UVB rays; look for ingredients such as titanium dioxide, zinc oxide, avobenzone and Mexoryl

Reapply sunscreen every 2 hours while in the sun

Apply at least one ounce (the size of a shot glass) of sunscreen to all exposed areas