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Time to sunburn

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Re: Time to sunburn

#11

Post by jandrese »

janci5243 wrote: post #2

This might be completely a common knowledge, but I just learned recently that SPF (the number on most sunscreen products) is actually a multiplier of the time you can spend in the sun without any protection So having an SPF of 50 increases a time 50 fold, which really puts things into perspective. Never leave the house around lunchtime without sunscreen.

Also remember however that the SPF numbers on most sunscreen are aspirational. They usually require you to apply a much heavier coat than most people think is reasonable and have shorter than you would expect full effectiveness window.

As the article discusses it also depends on your skin. If you are a fair ginger then yeah, sunscreen is your life. If you are more swarthy then you can get away with some midday sun.

Re: Time to sunburn

#12

Post by ihumanable »

janci5243 wrote: post #2

This might be completely a common knowledge, but I just learned recently that SPF (the number on most sunscreen products) is actually a multiplier of the time you can spend in the sun without any protection So having an SPF of 50 increases a time 50 fold, which really puts things into perspective. Never leave the house around lunchtime without sunscreen.

This is not correct, https://www.fda.gov/about-fda/center-drug-evaluation-and-res...

There is a popular misconception that SPF relates to time of solar exposure. For example, many consumers believe that, if they normally get sunburn in one hour, then an SPF 15 sunscreen allows them to stay in the sun 15 hours (i.e., 15 times longer) without getting sunburn. This is not true because SPF is not directly related to time of solar exposure but to amount of solar exposure. Although solar energy amount is related to solar exposure time, there are other factors that impact the amount of solar energy. For example, the intensity of the solar energy impacts the amount. The following exposures may result in the same amount of solar energy:

- one hour at 9:00 a.m.

- 15 minutes at 1:00 p.m.

Re: Time to sunburn

#13

Post by jandrese »

fouronnes3 wrote: post #8
Equiet wrote: post #5

There's a video which shows how you look like to a UV camera when you put sunscreen on. Also glasses with UV filters: https://www.youtube.com/watch?v=o9BqrSAHbTc

My ultimate dream is a pair of magical glasses with a small knob on it, which when turned adjusts the wavelength you can see from deep radio all the way to high energy gamma. Just imagine seeing the entire spectrum.

You want Geordi's VISOR from Star Trek.

Re: Time to sunburn

#16

Post by pmoriarty »

For those who, like me, started to wonder how using sunscreen affects vitamin D production, here's the conclusion of "The effect of sunscreen on vitamin D: a review":

"There is little evidence that sunscreen decreases 25(OH)D concentration when used in real-life settings, suggesting that concerns about vitamin D should not negate skin cancer prevention advice. However, there have been no trials of the high-SPF sunscreens that are now widely recommended. What's already known about this topic? Previous experimental studies suggest that sunscreen can block vitamin D production in the skin but use artificially generated ultraviolet radiation with a spectral output unlike that seen in terrestrial sunlight. Nonsystematic reviews of observational studies suggest that use in real life does not cause vitamin D deficiency. What does this study add? This study systematically reviewed all experimental studies, field trials and observational studies for the first time. While the experimental studies support the theoretical risk that sunscreen use may affect vitamin D, the weight of evidence from field trials and observational studies suggests that the risk is low. We highlight the lack of adequate evidence regarding use of the very high sun protection factor sunscreens that are now recommended and widely used."

https://pubmed.ncbi.nlm.nih.gov/30945275/

Re: Time to sunburn

#17

Post by version_five »

Equiet wrote: post #5

There's a video which shows how you look like to a UV camera when you put sunscreen on. Also glasses with UV filters: https://www.youtube.com/watch?v=o9BqrSAHbTc

The video was cool but I'd also be skeptical of how they imply that freckles (including UV spectrum freckles) are "damage" to the skin or undesirable. It's neat that people look different under UV, and it's a cool adaptation that our skin pigments seem to target UV differently that visible spectrum... that's all I would confidently take away from the video

Re: Time to sunburn

#18

Post by libraryatnight »

jandrese wrote: post #13
fouronnes3 wrote: post #8

Earlier quoted context omitted.

My ultimate dream is a pair of magical glasses with a small knob on it, which when turned adjusts the wavelength you can see from deep radio all the way to high energy gamma. Just imagine seeing the entire spectrum.

You want Geordi's VISOR from Star Trek.

The episode where they hook up his visor so they can display what he sees on screen was always cool to me.

Re: Time to sunburn

#19

Post by [deleted] »

Equiet wrote: post #5

There's a video which shows how you look like to a UV camera when you put sunscreen on. Also glasses with UV filters: https://www.youtube.com/watch?v=o9BqrSAHbTc

[deleted]
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