Have you ever heard this “rule”?
“Your skin absorbs 60% of everything you put on it.”
I see it all the time. The percentage may vary, but the idea is the same. Something goes on your skin and ZAP! It’s instantly absorbed possibly as deeply as your bloodstream.
Whether it’s meant to scare you or, almost as bad, it’s spread through ignorance, it’s simply not true.
Some things are absorbed deeply and quickly into your skin, but most are not.
Imagine taking a swim and absorbing 60% of the water that comes into contact with your skin. You’d swell up like a sponge and suddenly weigh so much you’d sink to the bottom like a stone.
Or spilling ice cream on your thigh and having 60% of it disappear right into your skin. Yikes!
Lucky for you, one of the many amazing things your skin does for you is to act as a barrier between you and the outside world. It also acts as your connection to the world, but we’ll talk more about that another day.
And yes, your skin does absorb things. But how much and what isn’t a simple percentage.
How much of a substance is absorbed into your skin is way more complicated
The 60% figure that you see all over the internet in marketing and blogs seems to come from a study that examined the absorption rates of industrial solvents like toluene, xylene, and methylene chloride (VOCs) in drinking water.1 The study concluded that 64% of these volatile organic compounds were absorbed through the skin.
I have two things to say about this:
- industrial solvents are designed to penetrate things that are harder to penetrate than skin
- I think we can all agree that avoiding skin contact with industrial solvents is a good idea.
When it comes to ingredients you put on your skin, there are a lot of variables that affect how much is absorbed and how much sits on and in the top layers of your epidermis.
Here are a few of the major factors:
- The size of the molecules that make up the ingredient
- how it enters your skin
- where you’re putting it on your body
- the condition of your skin barrier
Let’s start by looking at how your skin is made
One of the main jobs of your skin is to provide a barrier that keeps germs, dirt and debris and foreign substances out. Its design is brilliant.
There are several layers, each with it’s own job.
The outer layer is known as the epidermis. It’s your first line of defense in protecting your body from the outside world. It’s what you see when you look in the mirror.
Things to remember:
- the epidermis has no blood supply
- you shed about 500 million skin cells a day
Within the epidermis are 5 layers. New cells are made in the deepest layer and over the course of about 4 weeks (longer as you age) work their way up to the outer layers. By the time they arrive there, they’re flattened and essentially dead. These outer layers, called the stratum corneum, are 25-30 cells deep.
These outer layers are similar to a brick wall. The skin cells, called keratinocytes, are the bricks. The mortar that holds the cells together and helps form the barrier is a matrix of fats, cholesterol, ceramides and fatty acids.
Most of the products you put on your skin stay in the outer layers of the epidermis.
And that’s ok. That’s where they’re designed to work. They’re not absorbed into your blood (because they’re no blood supply to the epidermis), the molecules are too big to slip in between your epidermis cells and reach the deeper layers, and your skin sheds them off along with the dead cells each day.
Because the thickness of the skin (epidermis) is different on different areas of your body, this also affects how much of an ingredient is absorbed through your skin.
Places where the skin is thinner, like your face or the backs of your hands, absorb more product than, say, your back or the palms of your hand.
This is a good thing because it means your face, neck, and the back of your hands are able to make better use of active ingredients.
Below the surface (your skin's deep layers)
Below the epidermis is the dermis. The dermis helps to keep the epidermis intact and supports it with collagen and elastin.
The dermis also helps to communicate information from the outside layers to the rest of your body.
This area has a rich blood and nerve supply. It’s mostly made up of connective tissue (collagen and elastin). It contains your hair follicles, sweat glands, lymph vessels and the receptors that detect pressure, pain, and temperature.
The dermis is what gives your skin its firmness and elasticity.
To get through the epidermis and into the dermis, an ingredient needs to go through the skin cells, work its way around the cells through the oil based “mortar”, or through a sweat gland or hair follicle.
If your outer layers ( skin barrier) are disrupted or damaged (and this includes exfoliation), products will be absorbed more readily.
To be able to be absorbed into the deeper layers of the epidermis and dermis, the molecules of the ingredient also need to be small enough to move between or through the cells.
The general rule of thumb is that molecules need to be smaller than 500 daltons to penetrate your epidermis. This is really important for active ingredients. We want them to be able to reach the deeper layers and do their work.
Big molecules like collagen aren’t able to penetrate the skin at all. Small ones, like peptides and all trans retinol, can. This is why they can be so effective as active ingredients.
It’s not all good
Some ingredients are well absorbed and may not be so good for you.
I’m looking at you oxybenzone (a common sunscreen ingredient).
The other variable, and the one that’s really hard to measure, is how much of an ingredient is actually absorbed through the skin and into the bloodstream.
If it does make it into your bloodstream, does your body eliminate efficiently like it does with most of the myriad of waste products and toxins it encounters every day, or does it accumulate in your organs or fat cells?
Recent studies have shown that the sunscreen chemical oxybenzone is detected in the bloodstream at much higher levels than previously believed.
What this means is unclear at this point (but I’d advise caution and the use of a mineral sunscreen.)
The bottom line is that different ingredients are absorbed (or not absorbed) in different amounts depending on their molecular size, where on the skin they’re put, and the condition of the skin barrier. This can be a good thing or not, depending on the ingredient.
I’m not disputing that harmful substances can and are absorbed through the skin. I think we all need to be aware and careful of what we expose our skin to.
There are a few things (like solvents) that absorb at 60% or more, but for most skincare ingredients in most situations, it’s nowhere near that.
Obviously, we don’t want to take chances with ingredients we know aren’t good for us or even ones that are questionable.
But there are many effective skin care ingredients, both from nature and made in labs (or in a lot of cases natural based ingredients that are made into a form your skin can use in labs), that can really help our skin and are unlikely to end up any where but in the lower layers of your epidermis.