Hyaluronic Acid: Deeply Hydrating the Skin by Attracting Moisture
Hyaluronic acid (HA) has garnered a reputation as a superstar ingredient in skincare, thanks to its remarkable ability to hydrate the skin by attracting and retaining moisture. As cosmetic chemists, it's essential to understand the science behind HA, its various forms, and how to effectively incorporate it into skincare formulations.
What is Hyaluronic Acid?
Hyaluronic acid is a naturally occurring glycosaminoglycan, a type of molecule composed of repeating sugar units, found in the connective tissues of the human body. It's a key component of the extracellular matrix and plays a critical role in maintaining skin structure and moisture. The unique ability of HA to bind and retain water—up to 1,000 times its weight—makes it an unparalleled hydrator.
In the skin, HA exists in high concentrations in the dermis, where it helps to keep the tissue plump and hydrated. As we age, the natural production of HA in the skin decreases, leading to dryness, loss of elasticity, and the formation of fine lines and wrinkles. This decline underscores the importance of HA in skincare products aimed at moisturizing and anti-aging.
Forms of Hyaluronic Acid in Skincare
When formulating skincare products with HA, it's crucial to recognize that HA comes in various molecular weights, each offering different benefits:
High Molecular Weight Hyaluronic Acid (HMW-HA):
Molecular Weight: Typically >1,000 kDa.
Properties: HMW-HA sits on the surface of the skin, creating a protective, moisturizing barrier. It helps to reduce trans-epidermal water loss (TEWL) and provides an immediate hydrating effect, making the skin feel smooth and soft.
Usage: Best for products aimed at providing surface hydration and a protective layer.
Low Molecular Weight Hyaluronic Acid (LMW-HA):
Molecular Weight: Typically 50-1,000 kDa.
Properties: LMW-HA can penetrate deeper into the epidermis, delivering hydration at a deeper level. It is more effective for long-term skin hydration and can help to plump the skin, reducing the appearance of fine lines.
Usage: Ideal for anti-aging and hydrating serums that aim to deliver moisture beneath the skin’s surface.
Oligo-Hyaluronic Acid (Oligo-HA):
Molecular Weight: Typically <50 kDa.
Properties: The smallest molecular weight HA can penetrate the deepest layers of the skin. It offers profound hydration and can stimulate the production of new hyaluronic acid in the skin.
Usage: Used in advanced skincare products that target deep hydration and long-term anti-aging benefits.
Mechanism of Action: How HA Hydrates the Skin
HA’s primary mechanism of action is its ability to attract and retain water molecules. When applied to the skin, HA molecules draw moisture from the surrounding environment, including the air and the deeper layers of the skin (dermis), into the epidermis. This influx of moisture plumps up the skin, reducing the appearance of fine lines and wrinkles, and creating a smoother, more hydrated complexion.
The hydrating effects of HA are immediate, but they also offer long-term benefits. Consistent use of HA can improve the skin's overall moisture balance, strengthen the skin barrier, and enhance the skin’s resilience against environmental stressors.
Formulating with Hyaluronic Acid
When incorporating HA into a skincare formulation, there are several key considerations:
Concentration:
HA is effective even at low concentrations, typically ranging from 0.1% to 2%. Higher concentrations do not necessarily translate to better hydration and can lead to a sticky or tacky feel on the skin.
Molecular Weight Blend:
Combining different molecular weights of HA in a single formulation can provide both immediate surface hydration and long-term deeper hydration. This multi-layered approach maximizes the benefits of HA.
pH Level:
HA is stable and effective in a pH range of 4 to 7. It’s important to adjust the pH of the formulation to maintain the stability and efficacy of HA.
Synergistic Ingredients:
HA works well with other hydrating and skin barrier-supporting ingredients like glycerin, panthenol, and ceramides. These ingredients can enhance the moisturizing effects and improve skin texture.
Formulation Base:
HA can be incorporated into various product bases, including serums, creams, gels, and lotions. The choice of base depends on the desired product texture and target consumer.
Sample Formula: Hydrating Hyaluronic Acid Serum
Below is a simple yet effective formula for a hydrating serum that utilizes different molecular weights of hyaluronic acid to provide both surface and deep hydration:
Phase A:
Deionized Water - 85.00%
Glycerin - 5.00%
Sodium Hyaluronate (High Molecular Weight, 1,500 kDa) - 0.10%
Sodium Hyaluronate (Low Molecular Weight, 50 kDa) - 0.20%
Sodium Hyaluronate (Oligo, <50 kDa) - 0.10%
Phase B:
Panthenol (Pro-Vitamin B5) - 1.00%
Niacinamide (Vitamin B3) - 2.00%
Phase C:
Phenoxyethanol (and) Ethylhexylglycerin - 1.00%
Xanthan Gum - 0.30%
Tocopherol (Vitamin E) - 0.50%
Procedure:
Phase A Preparation:
In a clean, sanitized beaker, combine deionized water and glycerin. Stir until fully mixed.
Slowly add the Sodium Hyaluronate powders (High Molecular Weight, Low Molecular Weight, and Oligo) into the water/glycerin mixture, ensuring each one is fully dissolved before adding the next.
Continue stirring until the solution is homogenous.
Phase B Preparation:
In a separate beaker, combine Panthenol and Niacinamide. Stir until dissolved.
Phase C Preparation:
In another beaker, mix Phenoxyethanol (and) Ethylhexylglycerin with Xanthan Gum. Slowly add to Phase A under continuous stirring until the mixture begins to thicken.
Add Tocopherol to the mixture and continue stirring until fully incorporated.
Combine Phases:
Slowly add Phase B into Phase A+C under continuous stirring.
Continue stirring until the serum is homogenous and reaches the desired consistency.
Final Adjustments:
Check the pH of the serum. Adjust if necessary to a pH between 5.0 and 6.0 using a pH adjuster (e.g., Sodium Hydroxide or Citric Acid solution).
Packaging:
Once the formulation is stable and homogenous, transfer the serum into a suitable container, such as a glass dropper bottle.
Hyaluronic acid’s ability to deeply hydrate the skin by attracting and retaining moisture makes it a valuable ingredient in skincare formulations. By understanding the different molecular weights of HA and how they interact with the skin, cosmetic chemists can create effective products that offer both immediate and long-lasting hydration. The provided sample formula serves as a foundation for creating hydrating serums that can be tailored to meet various skincare needs.
Whether you’re formulating for surface hydration or targeting deeper skin layers, hyaluronic acid remains an essential component in achieving and maintaining healthy, hydrated skin. As you continue to explore and experiment with HA in your formulations, remember that the balance of ingredients, the choice of molecular weights, and the overall product design are key to delivering the best possible results to consumers.