Formulating on Trend: Barrier Repair

Moisturizers are a great format to include humectants, emollients and occlusives to help repair a damaged skin barrier. However, they are not the only option; serums and even toners that contain the right ingredients can help maintain the skin's barrier.

Featured: [podcast] Power Plants: Chicory, Sugarcane and Safflower Barrier Booster

Dryness is a common link between a damaged barrier and skin disorders including dermatitis, psoriasis, eczema and others. Dryness can cause redness, inflammation and flaking, all of which make the skin to feel irritated and unpleasant.

Moisturizers work to not only help maintain the skin barrier, but also to heal a compromised one. This property can assist with acne healing, in turn reducing scarring and skin aging. Moisturizers also impart a healthy and supple appearance.

Using a product like a moisturizer or a combination of products that contain humectants, emollients, occlusives and ceramides is the best line of defense to maintain and repair the skin barrier.

Skin Structure

As is well-known, the stratum corneum (SC) is the outermost layer of skin. It helps to protect the other layers (and the human body) from external factors such as UV rays, chemicals and pollutants. The SC also helps to maintain moisture and oil in the skin, to maintain health.

The stratum corneum is made up of a complex 3D structure consisting of:

• corneocytes, which are essentially dead cells;
• intercellular lamellar lipids, which help to reduce dehydration and increase moisture permeability;
• the cornified envelope, which creates a hydrophobic surface for water barrier function; and
• corneodesmosomes, which binds corneocytes together.

Within corneocytes are humectants that help maintain the hydration in the stratum corneum. These are often referred to as the natural moisturizing factor (NMF). Without an NMF, the 3D structure of the stratum corneum is easily damaged but the cornified envelope and lipid matrix help to reduce the loss of NMF. However, if the lipid matrix is compromised, this affects the NMF, which makes the skin barrier susceptible to damage. If the NMF is lost, the skin will retain unwanted skin attributes such as drying and flaking.

With the lack of NMF, the corneocytes shrink, causing cracking, inflammation and irritation to the skin. As such, the use of humectants in a skin care routine can assist in repairing lost NMF.

Humectants

When formulating with humectants, there are variety of options including glycerin, lactic acid, glycolic acid, propanediol and hyaluronic acid–all of which are water-soluble. Humectants can be used in creams, lotions, toners and serums.

• Glycerin: Helps to retain moisture and increases skin hydration, providing a cushion to the formula; but it can become sticky.
• Propanediol: This lighter version of glycerin helps to retain moisture and increase skin hydration. Propanediol has a lighter skin feel and generally has a less sticky feel than glycerin.
• Lactic acid/glycolic acid: These are AHAs and they act as chemical exfoliants and help to retain moisture. These acids do not usually affect the product's texture or feel.
• Hyaluronic acid: This ingredient helps to retain moisture, increase skin hydration and give the skin a supple and plump appearance. When used at low concentrations, it also does not affect the product's texture or feel.

These ingredients can be used in creams, lotions, toners and serums. Humectants are known to help draw moisture from the deeper layers of the skin to help hydrate the upper layers of the skin. However, since humectants are hygroscopic, they can also draw moisture from the environment, especially when the outdoor humidity is around 75-80%.

Archived: Profile of Glycerin

This can cause the reverse effect and even cause the skin to appear dry and dehydrated. To prevent this from happening, formulations can be combined with emollients and occlusives. 

Emollients

Emollients help soften and smooth the skin by filling voids between corneocytes. This, in turn, helps to protect skin from external factors. Examples of emollients include mineral oils, plant oils, vegetable oils and silicones.

Including emollients in the final formulation can help increase the efficacy of any humectants used while filling any voids in the lipid matrix. This imparts and overall healthy skin appearance.

Emollients help to reduce irritation, sooth inflammation and hydrate the skin. These attributes are great for not only maintaining the skin barrier, but also repairing the skin. Emollients are great additions to creams and lotions.

Occlusives

Occlusive agents function by forming a hydrophobic barrier to physically block and prevent transepidermal water loss. This is great for reinforcing the skin barrier because, as previously stated, water loss from the skin–especially when it comes to humectants–can cause adverse effects. Examples of occlusives include petrolatum and diisostearyl malate. Occlusives are great additions in creams and lotion and work well alongside emollients and humectants.

Ceramides

Ceramides are lipids that occur naturally in the top layers of skin, making up a significant part of it. Ceramides work by creating a protective layer on skin that helps hold the skin together. This helps to reduce moisture loss and, in turn, repair and/or maintain the skin barrier.

Related: Inside Ingredients: Ceramides

Skin disorders have been linked to an altered lipid barrier composition, specifically in terms of ceramide concentration, and a reduction in ceramides compromises the skin barrier. The addition of ceramides in formulations alongside humectants, occlusives and emollients can assist in barrier repair.¹

Examples of ceramides include Ceramide NP, Ceramide NG, Ceramide EOP, Ceramide NS, Ceramide AS and Ceramide AP.

Conclusion 

It is important to maintain the health of the skin barrier to prevent unwanted conditions such as dryness, flaking, premature aging, inflammation and irritation. Whether a person is experiencing skin concerns or they just want to maintain young and healthy-looking skin, maintaining a healthy skin barrier is important. Using a product like a moisturizer or a combination of products that contains humectants, emollients, occlusives and ceramides is the best line of defense to achieve this.

References

1. Coderch, L., López, O., de la Maza, A. and Parra, J.L. (2003). Ceramides and skin function. Available at: https://pubmed.ncbi.nlm.nih.gov/12553851/#:~:text=Ceramides%20are%20the%20major%20lipid,spaces%20of%20the%20stratum%20corneum.&text=It%20is%20generally%20accepted%20that,acids%2C%20cholesterol%2C%20and%20ceramides