: Why can the human body absorb toxins thru the skin, but you can’t rehydrate yourself by sitting in water?
In: Biology
So a large bulk of your skin is made up of keratin, a long fiberous protein. Imagine it weaving together like a woven basket. There’s still gaps in those woven threads however, so your skin has a layer of fat around and between the weaves of keratin. Water doesn’t dissolve into fat, so that layer of fat makes for a particularly effective barrier to prevent water from slipping through the keratin threads and into your body.
Some toxins however *can* dissolve into fats (like, for example, mercury). And on contact with your skin *those* chemicals dissolve into the fatty layer between the keratin weave and slip through.
So the human body doesn’t absorb “toxins” through the skin, but it can absorb *some* toxins, mainly those that are good at dissolving into fats.
Long and short, toxins can broadly be classifed as “water-soluble” and “fat-soluble” broadly, meaning “can be dissolved in water” and “can be dissolved in fat”.
Water is not fat-soluble. Meaning the fatty layer between the keratin bands will repel water. Some toxins *but not all* are fat-soluble (lead, mercury, certain pesticides, some drugs like fentanyl) meaning they can be dissolved into the fatty layer on your skin. If it’s not a fat-soluble toxin, then it can’t be absorbed by your skin because the fatty layer blocks it, just like it blocks water.
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