SPF - ah, the three letters that cover every sunscreen label. Everyone seems to think that a larger number should be better, but is that really true? What does the number even mean?
The ubiquitous three-letter abbreviation stands for Sun Protection Factor. Explained: it is how we measure a sunscreen’s level of effectiveness in blocking UV rays from your skin. Seems pretty simple, but there’s so much confusion surrounding sunscreen and SPF.
Let’s go back to basics first. Sunscreen is a topical product that is used to reflect or dissipate the sun’s UV radiation, which can cause a ton of bad things like sunburn, wrinkles, and skin cancer. It’s usually classified as either physical or chemical. The former often contains zinc oxide and titanium dioxide, but is thick and creates a literal barrier on your skin (hence the notorious white cast). Chemical sunscreens on the other hand are absorbed into your skin to dissipate UVA and UVB rays. Sounds awesome, but -- chemical sunscreens often contain oxybenzone which has been linked to cancer.
SPF is measured numerically, for example, Everyday’s Resting Beach Face sunscreen serum has an SPF of 30. The number is a measure of the fraction of UV rays that can reach your skin. In other words -- SPF 30 sunscreen indicates that 1/30 of UV rays will hit your skin’s surface, provided that you slather on enough (spoiler: most people don’t). One myth though -- a higher SPF number doesn’t necessarily mean it’s better. It’s been shown that anything over SPF50 is only minimally more effective, and that SPF usually measures protection against UVB rays and not UVA rays (more on that in a later article). Not only that, but the higher number seems to mislead people - so don’t let the number fool you!
Now that you know what you need to know about SPF - get outside and play, but don’t forget your sunscreen!