Eli5: Why do we need special lotions to moisturize our skin? Why isn’t the cure for dry skin just getting the affected area soaking wet everyday (showering)?
In: 15
Because you’re trying to replace *oils*, not water. Washing your skin with soap and water dries it out (see: dishpan hands) because it “cleans” the oils off of you
Moisturizers are not water-based; they are oil-based. Oil on your skin prevents dehydration because water evaporates and oil doesn’t. You don’t actually need special lotions; you could use margarine, if you wanted. You might smell a bit odd.
Dry skin isn’t lacking water, it’s lacking natural oils. Water washes the oils away, especially if soap or detergent is used, so it makes the problem worse.
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Dry skin gets dry because it is lacking in oils that act as a moisture barrier to keep the skin underneath hydrated.
Replacing these allows your skin to keep hydrated underneath.
Let’s get a few facts straight before we answer this question.
First in the US things like lotion are regulated by the FDA. I can only speak to that, as that is my experience.
Second, the word “cure” is operative here. As such, those lotions, for the most part do not cure or treat dry skin. *They only mask the symptoms.*
In the US for something to have a treatment effect, it is what’s called an “Over the counter Drug”. It has to have shown and demonstrated a function change in what the ailment is. A good example of a real functional cure is petrolatum for chapped lips. The FDA has a guideline at what levels can be used and how it’s labeled. If it’s a drug it will say, “Contains 80% by weight petrolatum”, if it’s not a drug, it will only have the ingredients listed.
What lotions typically do is use humectants to hold water against the skin reducing *the appearance of dry skin.*
Now you can put things into lotion that have a treatment effect without claiming the treatment. Dimethicone and petrolatum are used often in lotions for their humectant properties, but if you don’t make a claim, then they aren’t a treatment, and results may vary from person to person. Plus they have to be used at very specific levels, and often not at those levels.
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