3-O-Ethyl Ascorbic Acid (EAA) is a highly stable vitamin C derivative with a purity of over 99% and a low molecular weight of 204.18 Da. Owing to its favorable physicochemical properties, EAA efficiently penetrates the skin and reaches the dermis, helping to improve the appearance of stretch marks, keratosis, and uneven skin tone.
EAA remains chemically stable across a pH range of 3.0-6.0, making it compatible with a wide variety of cosmetic formulations. Supported by in vitro and clinical studies, EAA has been shown to promote collagen synthesis, inhibit tyrosinase activity, and reduce inflammatory markers, delivering consistent brightening and smoothing effects on large body areas—without the rapid oxidation seen in standard L-ascorbic acid.
Stretch Marks
Stretch marks are essentially physical ruptures of elastic and collagen fibers in the dermal layer of the skin.
EAA (3-O-Ethyl Ascorbic Acid), with a molecular weight of 204.18 Da, can penetrate the stratum corneum and reach the damaged area directly.
In vitro studies on Normal Human Dermal Fibroblasts (NHDF) showed that EAA treatment led to a >10-fold increase in collagen production compared with untreated controls, indicating strong potential for dermal regeneration.
Its high theoretical vitamin C equivalence of 84% supports the rapid fading of pigmented residues in early red streaks. Its stability in pH 3.0–6.0 environments ensures long-term efficacy, making it more suitable for sustained body care than L-ascorbic acid.
Reasons for Selection
In clinical dermatological observations, the repair of stretch marks mainly depends on the activity of fibroblasts.
The table below compares the technical performance of EAA with several common skin repair ingredients in treating streaks:
Measurement Dimension | 3-O-Ethyl Ascorbic Acid (EAA) | Pure Vitamin C (L-AA) | Vitamin A Alcohol (Retinol) |
VC Content/Conversion | 84% theoretical content | 100% (Direct action) | Not applicable |
Skin Permeability | Extremely high (Amphiphilic) | Low (Hydrophilic, difficult to penetrate) | Medium (Requires carrier coating) |
Light and Heat Stability | 90 days without discoloration at 45℃ | Extremely easy to oxidize and turn yellow | Extremely unstable when exposed to light |
Gentleness | Imperceptible in pH 5.5 environment | Stinging sensation below pH 3.0 | Easily causes desquamation and redness |
Treatment Methods for Different Stages
Changes in skin streaks usually follow an evolution from red (Striae Rubra) to white (Striae Alba).
The mechanism of action of EAA is supported by clear data at different stages:
1. Early Red Stage (Inflammatory Phase)
At this time, the streaks appear red or purple, mainly due to the expansion of microvessels in the dermis and inflammatory reactions.
Anti-inflammatory performance: EAA can inhibit the production of pro-inflammatory cytokines and reduce congestion in the streak area.
Pigment intervention: Used in the first 3-6 months of streak formation, it can prevent red pigment from converting into long-term dark brown pigment deposits.
2. Late White Stage (Atrophic Phase)
Streaks turning white means local tissue has undergone fibrosis, the skin has thinned and depressions have appeared.
Collagen filling: EAA can promote the synthesis of Pro-collagen (collagen precursor), filling physical depressions by increasing dermal thickness.
Elasticity reconstruction: Experimental data show that after continuous use of cream containing 2% EAA for 8 weeks, the skin's elasticity recovery rate is significantly improved.
Usage Details and Ratio
To allow EAA to reach the expected penetration depth on body skin, it is recommended to focus on the following physical details:
Recommended Concentration:
Preventive Care: 1.0% - 2.0% concentration, increases skin resilience.
Repair Care: 3.0% - 5.0% concentration, targeting clearly formed streaks.
Environmental Matching: The stratum corneum of body skin is 2-3 times thicker than that of the face. The amphiphilic (both water and oil soluble) structure of EAA allows it to enter deep layers without additional penetration enhancers.
Combination Suggestions: In high-end foreign body care formulations, EAA is often combined with 5% Madecassoside or 3% Squalane to simultaneously complete "fiber repair" and "lipid barrier replenishment."
Keratosis
Keratinized skin makes it difficult for ordinary ingredients to be absorbed due to barrier buildup.
EAA (3-O-Ethyl Ascorbic Acid) achieves penetration through its small hydrophilic and lipophilic molecular structure, with a melanin inhibition rate of 80.8% in the L-tyrosine stage and 89.1% in the L-DOPA stage, which can fade pigment deposits around hair follicles.
Tests confirm it can increase collagen levels in NHDF cells by more than 10 times, smoothing the rough texture.
A comparative stability study was conducted using a solution containing 200 mg/L of 3-O-ethyl ascorbic acid (EAA), L-ascorbic acid, and other vitamin C derivatives. After incubation at 43°C for 10 days, L-ascorbic acid retained only 10% of its initial activity, whereas EAA showed negligible degradation (<5%). This demonstrates significantly superior physicochemical stability compared with L-ascorbic acid, confirming its suitability for long-term repair of keratinized skin.
Performance in Addressing Keratinized Skin
Keratosis (commonly known as "chicken skin") mainly manifests as keratin buildup at the openings of hair follicles.
Ordinary skin care ingredients often stay on the surface, but the structural characteristics of EAA change this situation.
Permeability and Barrier Penetration
Skin in keratinized areas is thicker and drier than normal areas. EAA is amphiphilic, meaning it is soluble in both water and oil.
Physical Characteristics | Data Performance | Impact on Keratinized Skin |
Molecular Structure | Small hydrophilic and lipophilic molecules | Able to cross the thickened stratum corneum and act directly in the deep layers of the skin. |
Stability | Almost no degradation after storage at 43℃ for 10 days | Stable in complex body lotion formulations, it will not fail quickly like ordinary Vitamin C. |
Suitable Environment | pH 4.0-6.0 | Conforms to the weakly acidic environment on the skin surface, reducing irritation to existing inflammatory areas. |
Repair of Pigment Deposits
Perifollicular keratosis is often accompanied by reddish-brown or dark spots, which is caused by local oxidative reactions and melanin buildup.
EAA in this area is very specific in its test data:
Inhibition of Melanin Production: In the L-tyrosine test, the inhibition rate reaches 80.8%.
Blocking Color Transformation: In the L-DOPA stage, the inhibition rate increases to 89.1%.
Actual Effect: This high proportion of inhibition capability can make pigment deposits in keratinized areas less obvious after periodic use, making the overall skin tone look more even.
Underlying Smoothing of Skin Texture
Just removing surface keratin is not enough; keratinized skin needs to improve elasticity from the bottom to improve roughness.
According to test records of NHDF, EAA has a significant enhancement effect on skin structure:
It can induce more than 10 times the collagen production.
This enhancement can support collapsed or damaged skin tissue from within, and combined with its protective ability against UVB damage (DPPH free radical scavenging rate >70%), it can alleviate skin dryness and hardening caused by environmental factors.
Practical Application in Body Care Formulations
In the development of products for Keratosis, the following addition suggestions for EAA are as follows:
Addition Ratio: Recommended to use a concentration of 0.1% - 3.0% in the formulation.
Operation Process:
In aqueous products, it can be added directly and stirred.
In emulsified systems (such as body lotions), it needs to be dissolved in water first, and then added after the system has cooled to below 45℃ to ensure the activity of the ingredient.
Synergistic Performance: Although it is very gentle itself (Reconstructed Human Epidermis (RHE) skin model tests show high cell viability), when used in combination with gentle exfoliating ingredients, it can achieve the effect of first clearing surface buildup and then providing deep repair.
Body Brightening
Molecular Characteristics and Penetration Performance
An ethyl group is introduced into the molecular structure of EAA, which changes the physical property of traditional Vitamin C being extremely easy to oxidize.
In body care products, it does not need to rely on a strongly acidic environment below pH 3.5 like L-ascorbic acid to maintain its activity.
Characteristic Item | Experimental Data and Technical Details |
Molecular Stability | The degradation rate is less than 3% within 12 months under room temperature and dark conditions |
Partition Coefficient (Log P) | Approximately 1.2, showing good lipophilicity and easily passing through the lipid gaps of body skin |
Skin Irritation | Patch tests show that the irritation index at 5% concentration is close to 0 (physiological saline level) |
Metabolic Pathway | After entering the epidermis, it releases ascorbic acid through enzymatic reactions and directly participates in the biological cycle |
Melanin Control and Chromaticity Adjustment
Melanin deposits on body skin usually occur in joints, friction areas, or sun-exposed areas.
EAA improves coloration by intervening in the biochemical steps of melanin production.
Inhibition of Tyrosinase: Experiments show that a 0.5% EAA solution has an inhibition rate of over 40% on tyrosinase activity.
Reduction of Formed Pigments: It can reduce the formation of dopaquinone, thus limiting subsequent melanin synthesis, preventing the transport of melanin from the basal layer to the stratum corneum.
Improvement of UV Damage: Reducing the intensity of erythema caused by UVB irradiation, the red degree of the skin in the experimental group decreased by 20% after 24 hours of irradiation.
Application Suggestions for Different Concentrations
Based on the skin tolerance and dullness of different areas of the body, it is recommended to adopt a stepped addition ratio:
Low Concentration Solution (0.5% - 1.5%):
Mainly used for daily systemic maintenance. At this concentration, EAA performs basic antioxidant functions, clearing free radicals generated by environmental pollution, and maintaining the clarity of skin tone. It is suitable for addition to body sprays or large-capacity body lotions as a long-term skin conditioning method.
High Concentration Solution (2.0% - 5.0%):
Targeted at clearly visible local color blocks. For example, elbows, knees, or armpits. At this ratio, the collagen synthesis promotion function of EAA is activated, which can increase the thickness of the dermis and improve the dark appearance caused by thin or aging skin.
Formulation Compatibility and Stability Maintenance
When preparing body brightening products in the laboratory, the addition sequence of EAA and the environmental conditions will directly affect the shelf life of the final product.
Temperature Control: Add EAA active components during the cooling phase of the emulsification process (below 45°C).
pH Adjustment: Use sodium citrate or phosphate buffer systems to stabilize the finished product's pH at around 5.5, which is consistent with the acidity and alkalinity of the human skin surface.
Synergistic Combination: Combining with 0.2% Ferulic Acid or 1% Tocopheryl Acetate (Vitamin E) can further enhance its antioxidant performance in the aqueous phase, forming a circular protection chain.
