And how effective is it?
In: Chemistry
Sunblock works because there are compounds in it that absorb UV Rays, which are the light radiation rays that cause sunburns and increase your chances of skin cancer.
And for does it work, as a white person who spends lots of time outside, yes it absolutely works. I’ve had times where I didn’t put it on great and you could clearly see where I had and hadn’t put sunscreen on.
Edit: as for what the SPF numbers mean, say it normally takes you 10 minutes to start getting burned, wearing SPF 15 lets you spend 15 times longer outside before getting burned, so ideally 150minutes (buf things like sweating and going in water and washing some of it off will lower the amount of protective time)
Y’all are awesome. Thank you so much!
Light is a weird thing. It acts like a wave (think waves through water) and also like a particle (think marbles that bounce around). The smallest amount of light that you can have in one place is called a photon – think of photons as a particle of light. All light is made of photons, including light from the sun. Every photon has a certain amount of energy in it.
Some photons are visible to the human eye, this allows us to see! We can only see photons within a certain range of energy levels though. Infrared light (‘below red’, since it’s got less energy than red light) and ultraviolet light (‘above violet’, since it’s got more energy than violet light) are both invisible to the human eye.
Low energy light tends to get absorbed (in the form of heat) or reflected off of your skin (this determines what color your skin is). But high energy light – specifically ultraviolet light – can have enough energy to break apart the molecules in your skin. Not every UV photon will successfully break apart a molecule, but when you spend a couple hours in the sun, enough of them succeed for it to cause noticeable damage. Specifically, the UV photons damage your DNA, the blueprints for replicating your skin cells. When these blueprints get damaged, and your body tries to build more skin cells using the new cells end up wonky. Your body responds by destroying the wonky cells in a process called cell lysis. This prevents you from having too many wonky cells. This causes redness and irritation – a sunburn!
So how does sunblock prevent sunburn? It blocks the UV rays! It contains a molecule that either absorbs or reflects the ultraviolet photons before they can reach your skin. Sunscreen, when worn properly, is extremely effective.
SPF stands for “Sun Protection Factor”. It tells you the fraction of damaging photons that it lets through. So SPF 60 sunscreen let’s through 1 out of 60 damaging photons. In practical terms, this means that you can spend 60 times longer in the sun until you start to burn.
As far as efficacy, sunblock is the only anti-aging cream worth buying (and it *is worth buying*). Most people don’t apply it properly though and end up with less protection. Follow the directions on the bottle. Usually you must apply 1 hour before swimming and reapply every 30 minutes or something like that. If you follow the instructions (and get a friend to reach your back), you can spend a lot of time in the sun without getting burned.
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