ELI5 why the water in blisters doesn’t just seep out of the pores in the blister skin? If our skin is covered in holes, shouldn’t it leak? Especially if the blister skin is loose and dead?

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Your skin is waterproof, that means on the inside as well as outside. Pores aren’t holes straight through it, they lead down to sweat glands that are still part of the skin.


The same reason your blood doesn’t leak out of your pores. Your skin is an organ whose purpose is to keep the delicate moist bits of you on the inside, and the gross, dirty bits of the world on the outside. A regular friction blister is caused by shear stress which tears the epidermis away from the tissue beneath it, and the body reacts by filling it with ‘serum’, a mixture of water, protein, and nutrients, which help the underlying dermis heal. Don’t pop your blisters, you’re taking away the material your body needs to produce repaired skin.


The average % of water in a body is 60%. If your skin were porous, you’d be leaking all the time.


Kick a car. It now has a dent. That’s what a pore in our skin is, just deeper. It’s not a hole through the skin, it’s the skin itself that’s shaped like a hole.


Holes are holes, right? But if you think of the holes in your skin as being like the holes in a sponge, full of holes but with a little skin around them, then the water in the blister can’t just seep out through the holes because there’s skin in the way. The skin keeps the water in the blister. It’s like a little pouch of water that keeps all the water inside.