Humectants 101

Today’s post is about humectants, and Science, and mermaids. Mostly Science, though.

So what are humectants? Humectants are molecules that attract and bind water, much like a mermaid attracts sailors. Why should you care? Because hydrated skin is happy skin — water plumps up fine lines and wrinkles, resulting in smoother, younger-looking skin. (And it feels better, too.) Glycerin and hyaluronic acid are probably the most well-known, but there are plenty of others (honey, AHAs, etc).

This is metaphorical humectant molecule sitting on a metaphorical skin barrier.

You: “Wait if water is sailing around on water then isn’t it basically sailing around on the bodies of its fellow water pirates”

Me: shhhhhhh it’s a metaphor

When H20 meets up with topical hyaluronic acid, the H20 molecules hang out and hydrate the top layer of your skin.

Humectants are magic science!

I have dry skin, so I *love* moisturizers that include humectants. (Most often glycerin, but sometimes hyaluronic acid.) When The Ordinary came out with a Hyaluronic Acid + B5 potion ($6.80/oz), I had to have it.

Quick review of The Ordinary Hyaluronic Acid 2% + B5: it’s a clear goo in a glass bottle with dropper. This stuff does not “drip;” it “drizzles.” It is thick and viscous, and — though it absorbs pretty quickly — definitely leaves a sticky layer on your skin once applied. Normally I don’t mind a bit of tack (you can’t love snail secretion filtrate as much as I do and not be chill with tacky skincare), but this is a whooole other layer of sticky.

I took the texture as a good sign — if it’s really sticky, it must be really great at attracting water, right? So I applied the HA liberally, and — knowing how humectants work — I was expecting to wake up with bouncy, glowy, hydrated skin.

That did not happen.

The next morning my skin felt kind of … crusty? I’m sorry to use that word, but it’s really the only word for it — my skin felt drier and tighter, with a dried film on top. It was not ideal, to say the least. But I KNOW hyaluronic is a major hydration booster — it’s Science, y’all — and that everyone loves The Ordinary, so I persevered … and it happened again a second night, and then a third.


And then I had a lightbulb moment.

Science had not betrayed me. Science is WHY this was happening to me.

We tend to think of humectants as something that draws water to your skin; and for those who live in humid climates, where water molecules bounce around all the time, that’s what happens.

I do not live in a humid climate. I live in a mountain desert.

Here’s the other way humectants work.

If you have ever opened up a person, you’ll know they’re wet and squishy inside. Moisture travels from the lower levels of skin into the outer layers. When humectants are hanging out on top of your epidermis, the moisture in your skin goes to the outermost layer of your epidermis.

In a humid climate, this isn’t a big deal — humectants pull water out of the air AND up through your skin, so everyone is happy and hydrated together. Yay!

Now, when the landlubbers (skin moisture) gets to the top layer of the epidermis, they might want to leave the skin — but if there’s a lot of moisture in the air they’ll either be discouraged from evaporating, or it won’t be a big deal if they do — there’s plenty of alternative moisture for the humectants to ensnare.

But in a dry climate, water pulled up to the epidermis can evaporate — escape from your skin to the Great Unknown, leaving your skin drier than it would be without the humectant.

This is what happened to my skin.

So, knowing that there was insufficient moisture outside my skin, causing water inside my skin to force its way to the surface and evaporate, how did I fix it?

By adding water and a force field, of course! Instead of using the HA on its own, I put a very hydrating serum on top, followed by an occlusive “force field.”

This worked wonders. Next morning, my skin WAS bouncy and glowy and hydrated — more so than when I just used the serum and occlusive on its own, even. The hydrating serum had provided water for the humectants to pull into my skin, while the occlusive prevented the water in my skin from evaporating away.

Thanks, Science. I’m sorry I doubted you.

Who do you most closely identify with — Humectant Mermaid, Water Pirates, or Alien Occlusives? Please discuss scientifically.