The Truth Behind SPF and Sunscreens

Written by
July 15, 2023

SunscreenSummer is here but summer fun couldn’t be further away if your fun in the sun is being shadowed by questions about sunscreen. What strength do I use? How often do I reapply? What in the world do SPF numbers even mean? If I use SPF 30 and SPF 60, have I just created SPF 90? If these are the questions you ask yourself, keep reading!

How Does Sunscreen Work?

The sun emits both visible and invisible energy. One of the energy waves released by the sun is ultraviolet, or UV, rays. The UV rays sunscreen protects our skin from specifically UVB rays. But don’t think that sunscreen should only protect you from UVB rays. UVA rays can also cause damage to your skin with known effects being wrinkles and skin thinning. UVA can also play a role in causing skin cancers.

Sunscreens work by either preventing UV rays from penetrating your skin or facilitating a chemical reaction once UV has penetrated the top, dead layer of your skin and blocking the UV rays from passing further into your skin.

There’s More Than One Type of Sunscreen? 

Yes! Ignoring SPF ratings for a second, there are two types of sunscreens. Chemical sunscreens prevent UV rays from penetrating your skin further, and mineral sunscreens block UV rays from penetrating your skin.

Both chemical and mineral sunscreens can work well and provide the same SPF values.

What Is SPF?

SPF, or sun protection factor, is a measure of how much, calculated as a percentage of total rays, UVB rays a sunscreen blocks. But the numbers are not linear so SPF 60 wouldn’t be twice as effective as SPF 30. In fact, SPF 30 blocks about 97% of UVB rays, while SPF 70 blocks 98.5%.

When it comes to sunscreen, it isn’t just about the SPF, but the amount and frequency of application. Most sunscreens recommend reapplying every two hours, especially if you’re using chemical sunscreens that break down as the chemical reaction carries on.

I’m Still a Little Confused

If you’re still unsure about sunscreen, don’t get burned by a lack of knowledge! Call us at 301-656-SKIN(7546). We’re happy to help and educate. At Chevy Chase Dermatology, we make excellence a habit. Come see what sets us apart!

Category: Skin Care

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