Friday Weird Science: How much sun could a good beard block?

Sep 07 2012 Published by under Friday Weird Science

...ok I guess that probably won't work for some of us. Fake beards, maybe?


(I love the look on her face. Source)

I know a guy with a rather luxuriant amount of facial hair. I once asked him if he ever put sunblock on it. Get in the cracks, you know? He said of course not, hair blocks sun. He's never gotten a burn there, after all.

This is definitely true enough, I've never gotten a sunburn where my hair is, either. But how much sun does a good beard block if a good beard could block sun?

Answer? It blocks the sun that a good beard could block if a good beard could block sun.* At least, depending on the angle, and the thickness of the beard. But how to find out PRECISELY?!

Well for that you need SCIENCE. Science and fake heads with beards on them. On a weathervane. Really.

Parisi et al. "DOSIMETRIC INVESTIGATION OF THE SOLAR ERYTHEMAL
UV RADIATION PROTECTION PROVIDED BY BEARDS AND MOUSTACHES" Radiation Protection Dosimetry, 2012.

By now I think we all know the risks of UV radiation from the sun. Wear layers, slather on some SPF 30 until your skin can take no more, wear a hat, etc. But what about facial hair?

To investigate this point, the scientists in this study needed to look at the UV damage caused by the sun, at various angles, and with different lengths of facial hair. And since humans guys probably can't hold very still for the many hours it would take to measure this...well, this is what they built.


(I would have LOVED to see this thing hangin' out behind someone's lab on campus. Science in action, my friends!!)

They authors then looked at protection from UV radiation (using dosiometry, which measures dose exposure to UV radiation) at several angles of sunlight, and on several angles of chin, cheek, upper jaw, etc. They had a no beard condition, a "short" beard condition (10 mm on the upper lip, 40 mm on the chin), and a "long" beard condition (up to 20 mm on the upper lip and 90 mm on the chin). The beards were fake, as manikin heads have a terrible record of growing their own facial hair.

What you can see here is the exposure ratio, after 1 hour in the sun with the face angled up to receive the light (described as horizontal, they did 1 hour at most angles, except for the 25ish degree angle, which had 2 hours of exposure). You can see that beard presence significantly decreased the amount of UV exposure. When teased apart, the longer beards provided more protection.

So clearly, in addition to all our layers and sunblock, we need to be growing us some beards! Or, possibly, get fakes. There are of course caveats. Wither the stubble, my friends?! Wither the short goatee?! The "short" length here was 40mm long on the chin (almost 2 inches), which is pretty hefty, and the "long" was full on lumberjack. But most guys don't have facial hair that long, what protection, if any, are they getting? Does a couple of mm do any good? Or do we need to start a trend for some long and luxuriant facial locks?

Me, I think fake beards are going to be all the rage next summer.

Parisi AV, Turnbull DJ, Downs N, & Smith D (2012). Dosimetric investigation of the solar erythemal UV radiation protection provided by beards and moustaches. Radiation protection dosimetry, 150 (3), 278-82 PMID: 22090417

*How much wood could a woodchuck chuck if a woodchuck could chuck wood?

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