The Science Behind Hyaluronic Acid in Skin Treatments

What Is Hyaluronic Acid?

Hyaluronic acid (HA) is a naturally occurring glycosaminoglycan found throughout the body’s connective tissues. It is most concentrated in the skin, where it plays a critical role in maintaining hydration, volume, and structural integrity. A single gram of hyaluronic acid can hold up to six litres of water, making it one of nature’s most powerful humectants.

In younger skin, hyaluronic acid is abundantly present, contributing to that characteristic plump, dewy appearance. However, by age 50, the body’s natural HA levels have typically declined by approximately 50%, contributing to visible signs of ageing such as dryness, fine lines, and volume loss.

How Hyaluronic Acid Functions in the Skin

Hydration and Water Retention

The primary function of hyaluronic acid in the skin is water binding. HA molecules attract and retain water molecules from the surrounding environment, creating a reservoir of moisture within the dermal and epidermal layers. This hydration provides:

• Plumpness and volume: Well-hydrated skin appears fuller and more youthful
• Barrier support: Adequate hydration helps maintain the skin’s protective barrier function
• Nutrient transport: The water-rich HA matrix facilitates the movement of nutrients to skin cells
• Waste removal: Helps transport metabolic waste products away from skin cells

Structural Support

Beyond hydration, hyaluronic acid forms part of the extracellular matrix (ECM) — the structural framework that supports skin cells. Working alongside collagen and elastin, HA helps maintain skin firmness and resilience. It also acts as a scaffold for collagen fibres, supporting their organisation and function.

Wound Healing and Tissue Repair

Hyaluronic acid plays an important role in the body’s wound healing cascade. It regulates inflammation, promotes cell migration to the wound site, and supports the formation of new blood vessels. This property is relevant to understanding why HA-based treatments support skin recovery and regeneration.

Types of Hyaluronic Acid in Aesthetic Treatments

Topical Hyaluronic Acid (Skincare)

Topical HA in serums, moisturisers, and masks is the most accessible form. However, its effectiveness depends on molecular weight:

• High molecular weight HA (>1000 kDa): Sits on the skin surface, creating a moisture-binding film that reduces transepidermal water loss
• Low molecular weight HA (50-1000 kDa): Penetrates into the upper layers of the epidermis for deeper hydration
• Ultra-low molecular weight HA (<50 kDa): Can penetrate deeper but may trigger mild inflammatory responses that stimulate collagen production

The best topical HA products use a multi-molecular weight approach to provide both surface and deeper hydration.

Injectable Hyaluronic Acid (Dermal Fillers)

Injectable HA fillers are the most widely used dermal fillers worldwide. The HA in these products is cross-linked — a chemical process that links HA molecules together to create a gel that resists degradation and maintains its shape when injected beneath the skin.

Different degrees of cross-linking produce fillers with varying properties:

• Lightly cross-linked: Softer gels ideal for lips and fine lines
• Moderately cross-linked: Versatile gels suitable for nasolabial folds and moderate volume restoration
• Highly cross-linked: Firm gels designed for deep volumisation and structural support (cheeks, jawline, chin)

Bio-remodelling HA (Profhilo)

Products like Profhilo use a unique form of HA that is thermally cross-linked rather than chemically cross-linked. This creates a hybrid cooperative complex that disperses through tissue rather than staying in one place, stimulating collagen and elastin production across a wide area.

Mesotherapy and Skin Boosters

Skin boosters such as Juvederm Volite and Restylane Skinboosters use lightly cross-linked HA injected in micro-droplets across large areas of skin. Rather than adding volume, they improve overall skin quality, hydration, and smoothness.

The Manufacturing Process

Modern hyaluronic acid used in aesthetic treatments is produced through bacterial fermentation, typically using Streptococcus zooepidemicus bacteria. This biotechnological process produces HA that is:

• Biocompatible: Virtually identical to human HA, minimising the risk of allergic reactions
• Consistent: Manufactured under strict pharmaceutical conditions for reliable quality
• Scalable: Can be produced in large quantities without animal-derived ingredients

Historical HA products were derived from rooster combs, which carried a higher risk of allergic reactions. Modern bacterial fermentation has largely eliminated this concern.

Why Hyaluronic Acid Is Preferred for Fillers

Several properties make HA the gold standard material for dermal fillers:

• Reversibility: HA fillers can be dissolved with hyaluronidase enzyme if needed — an important safety feature not available with other filler materials
• Natural appearance: HA integrates with tissue and attracts water, creating natural-looking results
• Predictable behaviour: Well-characterised rheology (flow properties) allows practitioners to predict how the product will behave once injected
• Low immunogenicity: The risk of allergic reaction is very low due to HA’s biocompatibility
• Gradual degradation: HA is naturally broken down by the body’s own hyaluronidase enzymes, meaning results are temporary and require maintenance

The Future of Hyaluronic Acid in Aesthetics

Research continues to advance the applications of HA in aesthetic medicine. Emerging developments include:

• Next-generation bio-remodellers with enhanced collagen-stimulating properties
• HA-based delivery systems for topical application of active ingredients
• Combination products incorporating HA with other bioactive molecules such as polynucleotides or growth factors
• Personalised filler formulations tailored to individual skin types and treatment goals

Frequently Asked Questions

Is hyaluronic acid safe for all skin types?

Yes. Because HA is a substance naturally found in all human skin, it is well tolerated across all skin types and tones. Allergic reactions to purified HA are extremely rare. However, some HA products contain additional ingredients (such as lidocaine) that may cause sensitivity in some individuals.

Can you have too much hyaluronic acid?

In terms of topical application, HA is very safe to use daily. For injectables, over-treatment is a concern — too much filler can create an unnatural, overfilled appearance. This is a practitioner skill issue rather than a material safety issue. A conservative, gradual approach is always recommended.

Does taking HA supplements help skin?

Some clinical studies suggest that oral HA supplements (typically 120-240mg daily) may improve skin hydration and reduce fine wrinkles. However, the evidence is less robust than for topical or injectable HA, and the degree of benefit varies between individuals.

How long does injectable HA last?

Depending on the product, treatment area, and individual metabolism, HA fillers typically last 6 to 18 months. Lip fillers tend to metabolise faster (6-9 months) due to the high mobility of the area, while cheek and jawline fillers often last 12-18 months.

What happens when HA fillers wear off?

As the body naturally breaks down the HA, the treated area gradually returns to its pre-treatment state. There is a common myth that fillers stretch the skin and leave it worse than before — this is not supported by clinical evidence. If anything, the collagen stimulation associated with HA filler may leave a subtle lasting improvement even after the filler itself has been metabolised.