https://www.reddit.com/r/askscience/comments/1janev9/does_the_microbiome_of_the_human_skin_eyelash/
created by ScissorNightRam on 13/03/2025 at 21:33 UTC
1512 upvotes, 9 top-level comments (showing 9)
There are a lot of things that live on the human skin, and I'm wondering if humans can survive things they can't. Such as pressure, heat, etc.
So, for example, if you have a free driver who goes down to 100m, does that huge water pressure squasht all of a certain species in the dermal microbiome?
Comment by hexadecimaldump at 13/03/2025 at 22:05 UTC
1141 upvotes, 6 direct replies
Never completely killed off, but yes many things we do kill off large portions of our skin microbiome. The biggest of which is taking a bath or shower.
But the yeast and bacteria also live in our pores and other cracks and crevices of our skin that these activities can’t get to, so the microbiome does recolonize.
I listened to an interesting RadioLab episode about this where Robert talked about shaking JFKs hand when he was young and not wanting to wash it. Then they did a science experiment where he shook DeGrass Tyson’s hand, and they did a swab of each to see what microbes moved from one person to the other. It was a pretty interesting episode.
Comment by SpiritGuardTowz at 13/03/2025 at 22:16 UTC*
221 upvotes, 2 direct replies
Soap will probably kill and get rid of far more of them than any of the listed conditions. The sauna may do something but at that point I'd worry more about your own wellbeing. That pressure is largely inconsequent at those scales, ice will slow them down a bit but you'd be in risk of frostbite before you kill a significant portion off and "low oxygen conditions" isn't low enough for these creatures some of which can also happily live anaerobically.
Edit. This>these
Comment by jawshoeaw at 13/03/2025 at 23:44 UTC
63 upvotes, 0 direct replies
Your skin does have a microbiome but it’s not quite the same as say your colon or mouth. Your skin is an inhospitable desert. It’s dry and salty. It’s constantly flaking off too, which is instant death for anything attached to it.
In other words bacteria and yeasts are always dying on the skin. Going swimming, showering, using a sauna, all will remove or kill large numbers of organisms. But many of them were going to die anyway and they get replaced.
Comment by Turtledonuts at 14/03/2025 at 04:33 UTC
21 upvotes, 2 direct replies
Microbes are generally more resilient to harsh environments than your skin cells. They have less fragile cells and more complex defensive systems than a eukaryotic cell. If it doesn’t harm your skin, its generally unlikely to kill large amounts of microbes on your skin.
For example, microbes aren’t denatured by water pressure until far below the depths that a free diver can feasibly reach. If exposed to the kinds of cold temperatures that are needed to kill microbes, humans develop frostbite. Meanwhile, microbes can be defrosted and revive. Microbes have a lower and more variable metabolic rate, leading to lower oxygen requirements.
On the other hand, human skin is a lot more resistant to chemicals, to abrasion, and to high temperatures. Soak in a hot bath for hours and you might cook some microbes off. Soap and water does a lot of damage. Spray yourself with water and you’ll probably knock some off. Extremely hypotonic or hypertonic solutions can kill your skin microbes, as can fairly acidic solutions. I imagine a sunburn could cook off some microbes.
Comment by KwisatzHaderach55 at 14/03/2025 at 17:02 UTC
5 upvotes, 0 direct replies
Because several environmental and physicochemical parameters go beyond their tolerance gradient, like pressure, salinity, temperature, O2 levels...
They evolved sharing the same tolerance levels as their hosts, us. We go beyong the tolerance gradient, but for short periods of time.
Comment by RestaurantJolly1794 at 15/03/2025 at 02:29 UTC
2 upvotes, 0 direct replies
One of the main purposes of the skin is to act as a barrier against the environment, which means that it can protect against a variety of aggressors. Like heat, water loss, UV exposure, chemicals, etc. So naturally the skin microbiome is partially protected via the nature of the skin.
But also, because the skin itself is a relatively harsh microbial environment, the skin microbiome is very hardy and robust. The microbes thrive not only on the skin surface but within hair follicles and sweat glands and even into deeper skin layers.
So under more extreme conditions, the surface-level skin microbiota may be washed away or killed (although you’d be surprised, bacteria can be extremely hardy and resilient), but they will quickly be repopulated as they multiply and are pushed to the surface with sweat/sebum secretion.
Interestingly the skin microbiome was sampled from astronauts at the ISS and they saw that the microbiome changed over the course of the space mission. Whether that’s due to the impact of microgravity on microbial biochemistry or the conditions of the ISS (low microbial biomass/diversity, radiation, etc), it’s hard to know.
Comment by MilesTegTechRepair at 16/03/2025 at 00:17 UTC
2 upvotes, 0 direct replies
Ecological Succession is the process by which any ecosystem (and we can consider each human body it's own distinct ecosystem) that loses some or all of the species living within it. A good number of the species living in or on you may indeed be wiped out, but will frequently return, or regrow to their previous numbers.
I would be interested to hear about how our hygiene routines have affected the evolution of our various biomes.
Comment by Dog_From_Malta at 16/03/2025 at 15:30 UTC
2 upvotes, 0 direct replies
Tardigrades can survive extreme temperatures (from almost absolute zero to above the boiling point of water) , radiation and even the vacuum of space.
I wish you good luck in remaining alive while experiencing an event that would put a dent in their population.
Comment by lurkylarko at 15/03/2025 at 01:40 UTC
0 upvotes, 1 direct replies
You mentioned mountaineering. I’ve heard that spending time at extreme elevation can be detrimental to one’s mitochondria population. Not what we typically think of as microbiome, and applies to more than just skin, but it makes sense as those microbes are the essential component that metabolizes oxygen for cellular respiration.