SPF stands for sun protection factor and is a general measure of how long that particular sunscreen will protect you from ultraviolet (UV) B rays. UVB rays are different than UVA rays so it's important to get sun protection that is broad spectrum to help protect against both UVA and UVB rays.
So whats the difference anyway?
UVA rays are longer than UVB rays and can reach deeper into your skin's dermal layer. This can cause damage to collagen and elastic tissue. The damage caused by UVA rays is what gives skin that tanned look. Did you know that a tan is actually the skin's way of trying to prevent further damage? This attempt can lead to cell mutations which can trigger skin cancer. Not good.
UVB rays are the main cause of sunburn and can be difficult to gauge since the wavelength distribution of UVB rays can vary throughout the day. Even though there's no sunscreen that can block 100% of UVB rays, you can try your best by understanding some simple math. It's important to remember that the SPF number you see refers mainly to the amount of UVB protection it provides.
SPF 15 can block 93% of UVB rays
SPF 30 can block 97% of UVB rays
SPF 50 can block 98% of UVB rays
SPF 100 can block 99% of UVB rays
(Anything higher than SPF 100 is a gimmick and won't offer any better protection than products with a lower SPF. Reapplication is key!)
As you can see, SPF 30 does not mean twice as much protection as SPF 15. To further understand these measurements, you'll be pleased to know that tests have been performed to determine a sunscreen's SPF by seeing how long someone can be in the sun before they start burning. The test is then redone with sunscreen applied and the "with sunscreen" number is divided by the "without sunscreen" number then rounded down to the nearest five to determine the SPF.
If you want to figure out how long you can be in the sun with a given SPF, try using this simple equation:
Minutes it usually takes to burn without sunscreen x SPF number
= maximum sun exposure time
Generally speaking, if your skin begins to burn after 10 minutes of sun exposure without any protections, an SPF 30 sunscreen provides 30 times the protection than wearing no sunscreen at all. You can also count this as 300 minutes or five hours of protection before you begin to burn. If you have darker skin and take longer to burn than other fair skinned people, don't think you could do a day at the beach without layering on the sunscreen! While it's true the melanin in darker skin provides a natural protective layer from the sun, it isn't enough to forego proper sun safety.
Did you know that any scars or discolouration will get worse with increased sun exposure? That's one reason why EVERYONE should wear sunscreen. Yes I said it, every single person SHOULD. WEAR. SUNSCREEN.
You'd think the higher the SPF, the longer you can stay outside in the sun without getting burned right? Only in ideal situations of course. Many people forget that being outside also means being active. If you don't reapply your sunscreen after sweating or exposure to water, you will almost certainly suffer some damage. Regardless of the SPF factor, you should be reapplying every couple hours just to be on the safe side. A single application just won't cut it if you're going to be outside all day.
So tell me...how are other ways you protect your skin? I love wearing wide rimmed hats and staying in the shade as much as possible. Let me know how you enjoy the summer sun in a safe way. I'd love to hear from you!
Sources
https://www.consumerreports.org/cro/magazine/2015/05/what-does-spf-stand-for/index.htm
https://health.howstuffworks.com/skin-care/beauty/sun-care/spf.htm
https://news.psu.edu/story/141338/2010/06/01/research/probing-question-what-does-spf-rating-sunscreen-mean
super relevant! Now if only you could convince my hubby to wear it! :)
ReplyDelete