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Understanding Skin Absorption and Molecular Size

Understanding Skin Absorption and Molecular Size

Posted by Brendan Leonard with Dr. Hannah Sivak on Sep 21st 2021

This week, we’re celebrating the release of our Founder, Dr. Hannah Sivak’s new book, “The Scientific Revolution in Skin Care Second Edition.” So we thought that we’d take some time and work with her to really tackle a question that is deeply scientific, but that can also be used by skin care companies to influence the way we see the world.

Science is a funny thing. 

Really, at its core, the word science describes a practice. Science is the process by which we as thinking beings observe the nature of reality that surrounds us. We measure it, quantify it, and then we ask questions. With those questions in mind we build experiments and the outcomes of those experiments reveal to us more about the fundamental nature of reality.

But there are those that misinterpret not only how science works, but what science means. Sometimes you’ll encounter a person who says, “I believe in science.” That’s fine, that’s all well and good. Maybe when someone says that, what they are trying to say is: “I believe that we can understand more about the nature of reality through observation.” That works for us.

But when someone says, “I believe in science” and what they are trying to say is, “I believe in a world governed by indisputable facts” then we get a little uncomfortable. Because that’s not really the way that science works at all.

Science, as a discipline, is meant for questing intellects. Each question we seek to answer about the universe inevitably leads us to not only more questions but to deeper questions as well. Sometimes we find ourselves at a dead-end with a truth that was once taken for granted, and we realize that we made a mistake on the way. We have to rewind what we thought that we learned from science and restart the process of understanding to account for new material realities. 

This is a long way of saying, “our lived reality is made up of far more that we don’t know than we know.”

And this is a very long way of saying, “science reserves the right to change its mind.”

Skin Absorption

When you are researching skin care, you may encounter a lot of products making claims about skin absorption. The center of this concern is based around the physical size of individual molecules and whether or not they are too large to be absorbed into the cells that compose your skin.

So what are the real deal facts behind this concept? Can certain actives such as epidermal growth factor or hyaluronic acid be absorbed by the skin when applied topically? Or are you wasting your time and money, applying actives to your skin barrier?

The answer is more tricky than you might think.

The point of contention comes down to what many call the “500 Dalton Rule.”

The 500 Dalton Rule

The 500 Dalton Rule suggests that in order for a molecule to penetrate the skin barrier, its molecular weight must be less than 500 Daltons.

A Dalton, so that we are clear here, is a unit of measure for the incredibly small building blocks of the universe. Sometimes called a unified atomic mass unit, a Dalton is a unit of mass, meaning weight, of atoms used by chemists and physicists.

The problem with the “500 Dalton Rule” is that it’s not really a rule at all in the way that we think of them. This goes back to the concept of science delineating a series of hard and fast “rules” that apply in all situations. Once you start researching the 500 Dalton Rule itself you’ll find that there are a myriad of other factors that contribute to a molecule’s ability to penetrate the skin barrier. Some of the other factors include: 

  • The relative acidity of the molecule
  • The stability of the molecule 
  • The molecule's ability to bind with other molecules
  • And many more!

So what’s up with this “rule”, why does anybody use it?

Well, from a formulation perspective, it’s a great “rule of thumb” so to speak. When chemists and cosmeticists are working on a new formulation, it's easy to start with these generalities and then, as the formulation takes shape, experiment with even increasing specifics.

The problem is that some skincare brands want to use the 500 Dalton Rule to foment distrust of epidermal growth factor, hyaluronic acid and collagen based products from competing skin care companies. You’ll often see messages like this combined with access to their “patented formulas” or similar technobabble designed to insinuate that products containing these actives that are not produced by them are a waste of money. 

All we have to say to that is: “Well played Other Skincare Companies!” Because their strategies work. People then distrust the products that other companies sell. But at Skin Actives we’re about educating you to become your own skin health expert. We’re not afraid of you asking tough questions and we’re not afraid of delivering complex answers!

Skin Actives and Skin Absorption

So, after all that, what makes Skin Actives so certain that the specifics of our formulations will be useful and overcome the generalities of the 500 Dalton Rule.

Let’s hear from our Founder, Dr. Hannah Sivak:

“The outermost layer of the skin, the stratum corneum, limits water loss from the body to the environment and allows us, humans, organisms that depend totally on water, to walk around in the Arizona desert. The stratum corneum also limits water and chemicals penetration into the skin, slowing absorption of nutrients (and harmful chemicals) applied topically. 

‘Limits penetration’ doesn’t mean that this layer is impermeable, as shown by trans-epidermal water loss. You can measure water loss across the skin with a laboratory instrument, and this water loss increases with age and skin damage. In skin aged by sun exposure, absorption of external nutrients and water loss will be higher than in young skin.

Sometimes people cite a ‘rule’ that says molecules bigger than a specific molecular weight can’t enter the skin. There is no research proving that assertion, it’s just a “rule.” Some people keep forgetting that you need more than a theory (or a rule); science requires observation and experimentation.”

It can come as a surprise to many that the 500 Dalton Rule is still being experimented with in labs today. Scientists are still not sure if this “rule” is even a fact of material reality and are conducting experiments and writing papers to help us understand the truth of these interactions in nature.

Further, Dr. Sivak warns against using these “patented” actives that are broken down to smaller molecular weights:

“Giving our skin small pieces obtained by breaking up an active’s molecule may be counterproductive because they act as signals telling the skin that there has been damage and inflammation should ensue.”

If you’d like to hear more from Dr. Sivak about molecular absorption, check out her blog where she holds forth on all sorts of scientific subject matter in English and in a fully Espanol version as well!

So there you have it, Skin Actives Family: next time you see one of those sites that is trying to make your stomach clench with the fear that you’ve been using the “wrong” actives all this time, you’ll know the difference. 

We hope you take our word for it, but you can always check out the positive reviews Skin Actives has garnered with over a decade and a half of amazing results for our users of Collagen Serum, Hyaluronic Acid Serum, and the many epidermal growth factor products that we produce.

Join us back here this Friday when we take a look at “Skin Purging” the phenomenon you may have heard about recently and its relationship to acne blemishes. Thanks for reading Skin Actives Family, see you soon!