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When we have dry skin, we usually want to moisturize it.
Moisturize = water, so we have to give it water.
Ok, so far so good.
But when you give your skin water, by washing it or by going to the pool... 30 minutes
later, the skin is even drier than it was before.
Which should be nonsense when you when you think about it.
How can water, which is supposed to be the ultimate moisturizer, dry out the skin?
To think that water wouldn't moisturize the skin, that makes sense. When there's water on the skin,
obviously it doesn't end up getting absorbed by the body, it either
drops off or it evaporates.
Which is maybe not so bad, because because if we absorbed water this way,
you would come out all swollen after every swimming session.
So no, water does not enter the skin and in fact it doesn't hydrate it.
But for it to actively dry out the skin even more...?
That's overkill.
So why and how does water dry out our skin? And that raises another question.
If the skin is waterproof, then how do our moisturizers...
moisturize our skin? Why would it work better with them than with a tap?
Is the role of a moisturizer really to moisturize the skin?
Skin tightness, itchiness, flakes of dry skin falling off... all this stuff
is what I'm talking about when I say 'dry skin'.
So this is not a medical term at all but it represents the umbrella problem of
water lacking from our sking.
It is dry.
And guess who is less affected by dry skin problems?
People who live in the tropics.
Because there, the environment is super humid! So it's not just that our
skin absorbs the water that is in the air, but rather that the air is as
moist as our skin.
It's like two soaked sponges stuck to each other.
There is no exchange of water between because they are both soaked anyway.
On the other hand, if we are not in the tropics and the environment is rather dry...
Our skin will tend to wet the air... like a wet sponge stuck
to a completely dry sponge.
That's also why we have drier skin in the winter than in the summer.
In the winter, the sponge of the environment is very dry and we lose water, and
in the summer, the sponge is more humid so everything is in balance and we don't lose our water.
The simple solution to avoid this kind of exchange is to put a waterproof barrier between
the two sponges.
Which is exactly what the skin does.
You've seen this kind of illustration before.
There's stuff in this skin, but we don't need all this information today.
The only thing that interests us is to know that the skin is composed of a
layer on top, the epidermis which is quite thin, and a thick layer underneath,
the dermis.
And the epidermis is our waterproof barrier between our sponges.
Honestly, I see it as... a raincoat.
A skin raincoat.
A biological raincoat...
The epidermis is waterproof. A normal epidermis that works well and doesn't have
dry skin uses its keratin for that, which is a very hydrophobic protein and
which makes up the better part of the stratum corneum (upper layer), and also uses
intercellular bonds, a kind of cement that's between the cells of the epidermis, and
the third element of this impermeability is the hydrolipidic layer, so essentially
sebum, the fat that the skin produces.
Fat is very hydrophobic so it is very waterproof,
and this film, this layer that is put on top of the epidermis, it reinforces its impermeability.
The goal being that the water present in the dermis (the deep layer, the dermis being made
of flesh, approximately 70% water), this water cannot escape to the outside air.
The person you just saw is Audrey from the channel Dermato Drey.
She is a dermatologist and she also produces many videos on YouTube that I really
encourage you to go and watch as soon as possible.
What bothers me with what she's just explained is that our skin puts
all these mechanisms in place to protect us from this dry skin problem.
It's created a raincoat to prevent water from escaping.
So how come I, and maybe you watching, still have dry skin?
If the mechanisms are there, why don't they work ?
Genetically we are not all equal, some have stronger skin capabilities
that others.
People with atopic skin, prone to having eczema, asthma, hay fever etc
have barrier functions which are less effective.
In their skin, the secretion of sebum is less important, and the
sebum quality is also different. Adhesion molecules, the sort of cement
between molecules, are flawed too because of genetic anomalies.
So my raincoat is poorly made...
Having said that, this doesn't answer our first question which was: how come
it's worse after taking a shower? I asked Dermato Drey this question
and she used a pretty original analogy to explain this phenomenon to me...
Let me illustrate...
The dermis is like flesh, like a chicken cutlet let's say.
Note that I cooked it for hygienic reasons but this is supposed to be raw
in the demo so… use your imagination.
Above it, the epidermis is like dry puff pastry from a pastry like
a croissant. Normally this puff pastry is very oily.
There's no water that's supposed to pass through.
When we wet the epidermis, it is no longer 100% waterproof so it starts
filling up with water.
Besides, when you're having a bath, after a while you can see that the epidermis
is changed because your fingers are all wrinkled.
When you get out of the water, the skin gets dry, but by the time it dries completely,
the water that is present in the dermis will really want to go out through the skin layer
which is no longer very waterproof.
You can see here, it's like a cheap raincoat.
The first drops are retained, but beyond that, you quickly get soaked underneath
despite the presence of a raincoat.
Not great.
So, the croissant can't be saved, but the meat... I'll take it.
The epidermis, a very hydrophobic structure, doesn’t like being soaked in water.
As a result, when water manages to pass between the cells of the epidermis, by the time
that the epidermis gets dry, which takes about half an hour,
meanwhile we get out of the shower and have this gradient between the dry air from outside
and the dermis.
And since the epidermis is no longer perfectly greasy and perfectly hydrophobic, the water that
is in the dermis manages to come out.
So that's why our skin gets drier after taking a shower than it was before.
The epidermis, the raincoat (which is poor quality, remember), got so
soaked that that created a bridge for the water in the dermis (the deepest layer
of the skin) to escape.
So when the epidermis is wet, the water from the dermis leaks out very fast
into the atmosphere.
And when the epidermis finally dries up, the bridge between the dermis and the outside
closes and the evaporation is much slower.
So that's the effect of water ... but when we wash, there is also the effect
of the soap, which is not insignificant.
You know why we use dish soap to wash dishes?
It's to dissolve the grease that remains at the bottom of our pots.
The soap molecules catch the grease, surround it, and take it off with the rinsing water.
So the role of soap is to destroy the grease.
When we remove our natural grease, sebum, we lose our natural waterproofing
it is completely counterproductive.
It doesn't mean we should stop washing, but it means that washing our
hands with dish soap or with a strong soap may not be the idea
of the century if you already suffer from dry skin.
Which is a problem in these times of health crisis.
However, there are milder soaps which strip a little less fat, so you might
opt for those instead.
Let's keep washing, okay? That's the message.
So wash in moderation! And eat your 5 a day. *slogan confusion*
Well, this is all a bit discouraging.
It seems like conquering dry skin is a battle we can never win.
So what?
Shouldn't we just give up and learn to live with it? If it's not
not too uncomfortable, because it can be unbearable, so what
if we have dry skin after all?
Dry skin is often a source of discomfort: tingling, tightness, itching...
and then it can be the breeding ground for eczema too,
to the extent that, if all the intercellular bonds aren't there, nor is there a layer of sebum
as protection, the skin becomes like a colander and all kinds of small things
like pollen, mites, bits of dust can manage to get into the skin
and stimulate the immune system.
Normally on strong skin, they would have stayed outside.
Some viruses have a skin tropism, that is to say that they have the capacity to enter
the skin cell and modify it, like herpes viruses for example,
papillomavirus viruses, which give you warts.
Ok… I'll re-waterproof myself then.
I think you can guess what comes next.
Re-waterproofing is done through applying hydrating creams.
They're composed of a lot of fat, which in a way reproduces the layer of
sebum that is missing or incomplete on our skin.
Hence the fact that applying this kind of product... is a never-ending story.
We wash, which removes the sebum and the cream, so we put on the cream, then we wash again,
it removes the grease again, we put some cream back on... etc ...
The term "moisturizer" is not always well suited, because as we've said,
moisturizers don't necessarily hydrate the skin, but rather that prevent dehydration
by adding a layer of fat.
But also this term, “moisturizer”. The way I use it, I mean it as
a generic term for anything viscous believed to reduce dry skin problems.
And yet there is a real difference between milks, balms, ointments
and creams.
The fattiest type is the ointment, it's almost a 100% fatty phase.
Then you have balms, which are also pretty fatty.
When I say fatty, it doesn't necessarily feel like a fatty texture, people tend to
believe that it will be unpleasant but no, not necessarily—but there is more oily phase
in a balm than in a cream, more raincoat let's say...
If we make a classification from the most liquid to the fattiest, we have milks, then creams,
then balms, then ointments.
The closer you get to the ointment, the more fatty it is and the more it's made to add waterproofing.
We then rehydrate “from the inside”, in the sense that it is the water in our blood vessels
that water the dermis, and water can no longer escape because we have
put on an efficient raincoat thanks to the fat.
The more we move towards milk, the less waterproofing there is, but the more you will
nourish the epidermis of the skin (the superficial layer) something really hydrating
for the surface of the skin only.
There are people who need to apply urea, hydrophilic molecules,
I am thinking for example of keratosis pilaris, this is a problem in where
small bits of dead skin form some bumps, which makes the texture of the arms feel rough,
or grainy thighs, it's pretty common.
In this case we use urea which will be moisturizing and allows you to get
the small bits of skin off.
And on the other hand people who have atopic skin, who are prone to having eczema,
will instead use fattier products to hydrate them because it corresponds
to their lack in sebum, ceramides etc.
This is why all moisturizers are not suitable for everyone.
Before starting this video, I was probably like you.
I had bits of information, I knew a few things that we mentioned
in this video.
But with this discussion, Audrey really helped me clear a lot of things up.
Firstly, we naturally get dehydrated in a dry environment (especially
people who have dry skin problems); when the epidermis is wet, it allows
water from the dermis to escape more easily ; we strip our layer of
waterproofing when washing with soaps that are too strong and that's why
every day, we have to repeat this ritual of putting on cream
when we have dry skin.
Applying cream on the skin is not only useful because it's unpleasant
to have dry skin, but also because if we don't, we leave the door open to different pathogens.
And I also learned that the term "cream" that I used as something generic
is actually something specific and very different from an ointment or a
milk because of how it works on the skin.
Many thanks to Dermato Drey for responding to my questions. Our entire conversation,
which is 45 minutes long, will be available on her channel in a few days (on Sunday),
I will put the link in the description then.
In the meantime you can already discover her channel and watch all of her videos.
She talks about dermatology, as you may have gathered, so go check it out, and subscribe
while you're at it.
With that, I think... I think it's time.
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Well here it is, I hope you have all learned something about moisturizers and
about how our skin hydrates and becomes dehydrated.
I'll see you in the next video.
Bye!