Transdermal Technology

Fick’s Law of diffusion and how topical ingredients can be delivered

Written By: WETHRIVV

Your skin is your body’s biggest organ. It breathes, and it is constantly exchanging nutrients and toxins from the surrounding environment. 

Your skin may be thought of as a water bag. If you forget about your sweat glands for a moment, the skin does not readily allow water to exit the body. This barrier against the movement of water is due to the tiny bit of fat at the base of the skin. 

The top layers of your skin are made of a substance called phospholipid. Just below the phospholipid layer is the fat I just mentioned. Fat does not mix with water. You may have noticed this when cooking, making a salad dressing or a stir fry. 

Fat won’t mix with water, but it will mix with other types of fats. 

So how does water make your skin prune when your hands are in water for a long time? The uppermost layer of phospholipid on your skin will absorb a little water and cause the pruning effect. But the water won’t cross that fat barrier in the deeper layers.

The phospholipid layer will also absorb oils and fats too. Ultimately, any nutrient that will absorb into oil will get into the skin’s first layer. It is quite a versatile layer. 

This means that some of the nutrients that we apply to the skin, such as vitamin E, will absorb into the phospholipid layer, because it also mixes with oil. But it doesn’t stop there!

The lower fat layer of your skin will absorb any nutrients that mix with oil. There are many important nutrients that your skin will absorb, first into the phospholipid layer, then afterwards into and across that fat layer.

But how exactly does a nutrient travel from the surface of your skin to the deeper layers and onward? 

Fick’s law of diffusion states that molecules move from higher concentration to places of lower concentration. For example, when you open a bottle of perfume, people can smell it from the other side of the room. The scent moves from the highly concentrated bottle to the other side of the room where the concentration is low. 

Fick’s law also applies to the skin. If you apply your serum to the surface of the skin, it is highly concentrated above the phospholipid layer, and it wants to move into the fat layers lower in your skin, where its concentration is lower. 

But when the two sides of the skin become equally concentrated, Fick’s law dictates that the nutrients stop moving. This is good because it prevents you from getting too much of a good thing. This is how nature has protected us. 

Thus, the ultimate face mask will have a concentration of nutrients that are not to low, not too high, just right. This is the science that goes into making the MASKAD products from WETHRIVV. 

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