Seems to me like we should’ve easily invented something that lasts indefinitely by now
In: Chemistry
We could, but it would have other downsides.
Like being way [too opaque and sticky.](https://youtu.be/8oJzfmWO3CU?si=eVILZizWWc0zJ67r)
Go buy an old man travel shirt. You know the kind with the vent in the back. I wear one whenever I do yard work for a while cause I don’t like sunscreen.
There are two kinds of sunscreens. Chemical sunscreens which are absorbed into the skin. And physical sunscreens, which leave a residue on top of your skin. of of zinc or other minerals that reflect the UV rays away from your skin.
In the case of chemical sunscreens, the chemicals start to break down when exposed to air. So they are only adequately protective for a couple of hours. In the case of physical sunscreens. Moving around, sweat, clothes, etc. can displace the minerals, and leave you with spots that are unprotected. Reapplication every couple of hours solves both problems.
I think the real question is why can’t we make a sunscreen that lasts a whole day, long enough that you don’t need to actually reapply it for a whole day activity, instead of just two hours or being extremely difficult to remove without special chemicals, neither of which seems desirable.
A little bit of cream isn’t going to block the radiant energy from the most massive object in our solar system for very long.
Evy claim to have invented a sunscreen that lasts 6+ hours, there is a review here which talks a bit about the science. As an example, the more the sunscreen is absorbed into the skin the less it protects the outside of the skin – but the less it’s absorbed the easier it is to have it wash or rub off – as an example of the challenge:
[https://labmuffin.com/do-they-work-evy-6-hour-sunscreen-dermablend-drops-in-spf/](https://labmuffin.com/do-they-work-evy-6-hour-sunscreen-dermablend-drops-in-spf/)
I have also seen another sunscreen that claims to also be much longer lasting but sortof does so by layering on top of the skin but forming more of a permanent film. I don’t recall the name. However those are still easily rubbed off mechanically.
Traditional sunscreens can also sometimes last longer than 2-4 hours, but they have to give guidelines that apply to everyone whether you’re sweaty, swimming, doing something abrasive where you rub against things, etc plus work for people that under-apply versus those that over-apply, etc.
If you want to learn more about sunscreen from a mechanism/science perspective her YouTube channel is great. I’m sure she’s not perfect but you’ll learn more than you’d be likely to otherwise.
Latest Answers