If you’ve just been in water why are you rehydrating your skin?
In: Biology
Because water from pools and sea has lots of solutes there. You might actually think because you got wet you are hydrated but its not enough. Law of osmosis states that water moves from area of low concentration to high concentration so water actually moves from your skin to nearby water. Hence wee moisturize.
Especially when bathing, we generally use soap and warm/hot water, both of which strip away the oils that are the skin’s natural protection against drying out. Until these oils are replaced, either naturally or by applying moisturizer, the skin loses moisture through evaporation.
The moisture is not lost through osmosis- at least with general bathing conditions, since the solute concentrations in bodily fluids are far higher than in tap water- meaning that the osmotic pressure would actually favor driving water into the body, rather than pulling it out.
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