The 60% rule

The 60% rule

“Your skin absorbs 60% of everything you put on it.” I sighed and slammed the laptop shut.

Whether it’s meant to scare you or spread through ignorance, outright misleading or wrong information makes me crazy.

But then a vision popped into my head and I started to laugh.

Imagine taking swim and absorbing 60% of the water that comes into contact with your skin. You’d 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 into your skin.

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.

It’s 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 think we can all agree that avoiding skin contact with industrial solvents is a good idea.

When it comes to ingredients you actually want to 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.

The outer layer is known as the epidermis. It’s what you see when you look in the mirror.

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.

Things to remember:

  1. the epidermis has no blood supply
  2. you shed about 500 million skin cells a day

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) 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.

Below the surface

Below the epidermis is the dermis. 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 skin barrier is 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 need to be small enough to move between or through the cells.

Big molecules like collagen aren’t able to penetrate the skin at all. Small ones, like peptides, can. This is why they can be effective as active ingredients.

Unfortunately, some ingredients are well absorbed and may not be so good for you. I’m looking at you oxybenzone (a common sunscreen ingredient).

What gets into your bloodstream?

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.  

And 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.

The upside

The upside is that we can use our existing knowledge of how your skin absorbs ingredients to get better results from skin care products.

 

We know that the “mortar” between your skin cells is oil based. That means that oil and butters can penetrate and be absorbed through this matrix.

You may have noticed that if you have dry or dehydrated skin, using a facial oil alone won’t make your skin feel moist.

This is because oils aren’t well absorbed into skin cells, which are mostly water.

 A better approach is to harness the powers of both water and oil based ingredients using a moisturizer. Moisturizers are typically emulsions. Emulsions contain both water and oil based ingredients bound together with an emulsifier.

Moisturizers like SunUp and SunDown give you the benefits of both cell and matrix penetration (into the epidermis, generally not the deeper layers) and have the added bonus of delivering active ingredients.

Once your skin is hydrated, you can use a light layer of facial oil to seal in your skin’s hydration and deliver additional nutrients. The oil will actually be more effective this way.

 References

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1651599/?page=1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


4 comments

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  • Dr. Holly

    Thanks. Glad you found it interesting

  • Pat

    Very interesting, I plan to read previous posts before launching a new skin care program.


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