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Humectants

What is a Humectant?

Humectants are a collection of ingredients in skincare that can be incorporated in serums and moisturizers, and can also be one-off ingredients, like Hyaluronic Acid or Glycerin.

Humectants are Misunderstood

Skin doesn’t crack or break when exposed to extremely cold temperatures, and that’s because of the humectants that are naturally present. These humectants are the same “anti-freeze” that are used in many different applications to keep the skin flexible and supple. It’s a common misconception that humectants are good for hydration because they hold water in the skin. This understanding would mean that the humectant that would be the best hydrator would be the one to hold the most water. This has been clinically proved to be incorrect. Glycerin, which holds three times less water than sodium pca, is a better humectant as it shows better results.

 

 

How do Humectants Work in the Skin?


There are three types of water in the skin:

 

1. Tightly bound

  • This is permanent and tightly bound to cells

2. Loosely bound (we want more of this!)

  • Bound by keratin, MFA (humectants in the skin) and lipids, and dictated by the interactions of these three.

3. Free water

  • Flows from the deeper layers of the skin to the upper most layer and evaporates

Good, hydrated and not dry skin, has a higher percentage of loosely bound water. This is also the type of water in the skin that can be altered with ingredients.  

The Previous Model for Hydration: 

Previously, it was believed that NMF, Keratin and Lamellar Lipids were the most important because they dictate the bound water portion in skin. NMFs act like skin sponges inside the skin cells. Hydration levels are mostly dictated by keratin and NMFs. Keratin can bind water, but only at high percentages.

The Newer Model for Hydration:

Recent thinking suggests something different. NMFs have been found to be able to affect keratin and lamellar lipids. The main function of humectants isn’t that they hold water, it’s that they replace water in your skin. Even when water evaporates, humectants remain. Humectants stay on the skin because they have lower vapor pressure. They are less susceptible to evaporation than water.

When you have a very low amount of water in your skin, it’s dry, flaky and it cracks. When you move towards the maximum amount of water in the skin, keratin fibres open up to bind water in them.

Picture dry skin like dry noodles - it can easily crack and break. Nobody wants that. Once absorbed with water, it’s flexible and pliable. Yes please! 

 

Can I have some examples please? 

Humectants like glycerin or urea can actually replace water in keratin. They can bind water at lower relative humidity and make keratin pliable by binding to it. Keratin is pliable because it’s stretched out; once humectants are placed in the skin they bind to the skin at lower temperatures and cause skin to be more soft. If water binds to keratin at 50%, the addition of urea or glycerin causes the skin to be more pliable. So instead of NMFs holding water, they replace water. 


How do humectants cause a change in barrier lipids?

We have to rethink humectants based on their effect on proteins and lipids. Barrier lipids can be understood as the cement in between layers of the skin. In 30% relative humidity - so, not a lot of water in the skin - the short layers of the barrier lipids have a tight structure. There’s very little water in between them. This is called the orthorhombic structure - picture a container tightly packed with lollipops. This can be a good thing in terms of permeability because nothing can pass through them, but too much of this structure is not a good thing. It causes the lamellar layer to be brittle and so the skin can easily be broken.

 

As the relative humidity increases, water gets into the lamellar lipids and also gets in between the ceramide heads. This makes the lamellar layers more flowy. Flowy, supple, flexible, smooth skin… Yes please. 


NMFs or humectants are able to bind in between lamellar lipids and able to cause conformational change - meaning they cause lamellar lipids to flow. Skin can have the appearance of being full of water even when the water levels are low.


Different types of humectants have different effects on the skin, which is why we've packed our hydrating serum Wave with 24 of them. 

 

Humectant

Usage Rate

Skin Function

Glycerin Up to 100%
  • Aids in degradation of corneodesmosomes
  • Enhances the transglutaminase mediated corneocyte envelope cross linking
  • Induces Barrier lipid production
  • Promotes Ceramide esterification
  • Countless more
Urea 5-30%
  • Aids in degradation of corneodesmosomes
Hyaluronic acid 1-2%
  • Biochemical messenger
Lactic acid 2-30%
  • Aids in degradation of corneodesmosomes
  • Induces Barrier lipid production
Osmolytes (Betaine, Taurine, Myoinositol) 2-5%
  • Protect Tight Junctions
  • Increases available free water
Sodium/Potassium Lactate 2-5%
  • Binds to amino acids in Keratin
Sodium PCA 1-10%
  • Targets free water in SC
Amino Acids Up to 100%
  • Various Functions
Sugars
Up to 100%
  • Induce Barrier Component production
Ions
No data
  • Aids in interaction of NMF and proteins
Sugar Alcohols (Sorbitol, Xylitol, Mannitol) Depends on the sugar alcohol
  • Promotes production of barrier components
  • Inhibits Biofilm formation
  • UV-protection
  • Prebiotic
Glycols Depends on the glycol
  • Antimicrobial effect
  • Penetration enhancer

 

 

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