It’s the dead of winter.
And… well, you know what that means:
curling up with some hot cocoa,
watching friends on Netflix and
staring at your dry, cracked skin.
Wait, what?
[Reactions intro]
When temperatures drop and heaters kick on,
indoor air gets drier.
That sends many of us scrambling for
a moisturizer to ease the unsightly
and irritating effects of dry skin.
But what do these products actually do?
As the name suggests, their job is
to make your skin more moist.
Skin dries out by a normal process with a
fancy scientific name: transepidermal water loss.
Or, if you like funny-sounding abbreviations, tewl.
Blood vessels only supply moisture to
the middle layer of skin, the dermis.
From there, water moves outward through
to the epidermis before it evaporates.
A moisturizer’s job is to trap or replenish
the moisture in the epidermal layer.
Moisturizers come in three varieties:
occlusives, emollients and humectants.
Most products you buy have a
combination of some or all of these.
Occlusives are the old school moisturizers,
and they work in the simplest way possible.
They form a barrier over the skin that water
can’t penetrate, stopping evaporation
and keeping your skin moist.
The best in the biz is petroleum jelly, sold as vaseline.
It cuts tewl by 98 percent.
The long carbon chains of the molecules
that make up occlusives repulse water.
The only problem?
You don’t really want to walk around covered in vaseline.
We hope.
More popular these days are the emollients.
Instead of coating the skin, these are
designed to penetrate, making skin
feel softer and more flexible.
They are made from similar chemicals as
occlusives: molecules with long fatty
carbon chains like stearates and castor oil.
But they work differently.
The outermost layer of your skin has a
‘brick-and-mortar’ structure where the bricks are
dead cells, called corneocytes, and the mortar
is made of fatty layers of lipids.
Corneocytes are linked by proteins that form a
strong barrier between your body and the bacteria,
microbes and toxins in the outside world.
The ‘brick-and-mortar’ stacks are thicker
in places like your palms, but thinner
on softer skin like your face.
When the moisture level in the air goes down,
the protein links break apart and fractures
develop between groups of corneocytes.
Emollients get beneath the skin’s surface
and fill in these gaps, keeping tewl
under control and helping your skin feel smooth.
The third kind of moisturizers are humectants.
Broadly, these molecules help attract
and retain moisture in the epidermis.
Humectants help get the younger, moist cells
towards the outer layer of skin, as well
as reduce the flakiness of dry skin.
Humectants also stimulate the body’s
natural production of ceramides,
waxy molecules that reduce tewl.
So don’t leave your skin out to dry this winter.
Grab some lotion and stay hydrated.
Your corneocytes will thank you.
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