Beauty, Health, Lifestyle, Skincare

The Science Behind SPF

The Science Behind SPF

Since summer is pretty much here, I wanted to talk a little bit about sunscreen. We all know that we should be wearing it, and we know that it protects us from getting sunburned. How does it really work though? Is the idea that more SPF is better, really the right idea, or are you maybe paying a premium for (almost) nothing?

So first of all. What is SPF? A sunscreen’s sun protection factor is an (in my opinion somewhat misleading) way to classify how well a sunscreen will protect from UVB rays. It is often explained as a multiple of the length of time that you can stay in the sun without getting burned. Usually, this number is about half an hour, which means that an SPF 30 would protect you for 15 hours and an SPF of 45 would protect you literally ALL DAY. (Spoiler alert: that’s not actually how it works).

A sunscreen with an SPF of 15 blocks about 94% of UVB rays; SPF 30 blocks 97% of UVB rays; and SPF 45 blocks 98% of UVB rays. These are the rays that burn your skin, but UVA rays are responsible for a lot of the sun damage to the skin. No matter what level of protection you choose, make sure that you pick something with a PA+++ if it’s available. If you can’t find anything that uses this measurement (as it’s not universal), pick something with broad spectrum protection. This is what will prevent the most damage to your skin.

How long this protection lasts, though, is really not so simple. While in a perfect world, it may work in the way I described above, the reality is a bit different. The length of time that a sunscreen will work as well as how well it will work will vary based on several factors. These include how much sunscreen you’re actually applying, the weather, how much you sweat, and if you swim and how well you towel off afterwards.

So what does this mean? Any sunscreen over SPF 50 is probably not worth the extra expense. You should be reapplying your sunscreen every 2-3 hours, regardless of what the SPF is. This means your face, too! I will be writing a post in the future about my favourite sunscreens and how to manage them with a full face of makeup.

What type of sunscreen do you use? Do you think it’s worth it to pay more for a higher SPF? Let me know in the comments or tag me on social media!


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