Source: flickr.com user brianauer

As one of the palest of the pale, I’ve heard it my entire life – wear sunscreen! Applying an SPF if one of the most important beauty tips out there. So important, in fact, that many makeup and skin care formulations now include an SPF to give your skin an extra layer of protection. But, why? What is this all-important SPF, and why should you protect your skin against ultraviolet damage?

To understand why protecting your skin with an SPF is so important, all you need to do is understand what UV rays are and what they can do to your skin. After you’ve learned all the scary details, I doubt you’ll ever forget to wear your sunscreen again!

UVA
UVA rays are the age-accelerating rays, which is easy to remember by thinking of them as UVAging rays. UVA rays damage collagen fibers, destroy vitamin A, and cause free radicals and reactive oxygen species. Although UVA rays do not directly damage DNA like UVB and UVC rays, they can contribute to DNA damage by creating hydroxyl and oxygen radicals. 98.7% of the UV radiation that reaches the Earth is UVA, which makes it extremely important to make sure that you’re using a sunscreen or sunscreen moisturizer that protects against UVA damage.

UVB
Think UVBurning rays, as these rays are the ones responsible for sunburn. Like UVA rays, UVB rays damage collagen fibers and destroy vitamin A, although at a much slower rate than UVA rays. Sound less aggressive than UVA rays? Not quite. UVB rays are capable of directly damaging DNA and causing the mutations that may lead to skin cancer.

UVC
UVC rays are the most dangerous type of ultraviolet light. Thankfully, UVC rays are thoroughly filtered out by the atmosphere, which means we don’t need to worry about them!

SPF and PA
All sunscreens have an SPF (sun protection factor) rating. An SPF rating refers to the level of protection that particular formula gives you against UVB damage, but it doesn’t tell you anything about the level of protection it provides against UVA damage.

Currently, the US doesn’t have its own rating system for UVA rays, although you’ll sometimes see the Japanese rating system, known as the PA system. The PA system uses the Persistent Pigment Darkening (PPD) method to measure UVA protection. There are three common levels of PA ratings – PA+, which provides some protection, PA++, which provides moderate protection, and PA+++, which provides good protection.

If your sunscreen doesn’t have a PA rating, that does not necessarily mean that it doesn’t protect against UVA damage. Ingredients such as zinc oxide, titanium dioxide and avobenzone shield against UVA damage, so be sure to check the ingredients of your current sunscreen formulation before heading out to search for a replacement.