COSRX THE VITAMIN C 23 SERUM 20ML

Values You Can Trust: Halal-Friendly* / Vegan-Friendly* / Cruelty-Free / 100% Authentic Guarantee

*Self-assessed by Adilsons based on available ingredient data (no ethanol/denat.; no haram animal-derived ingredients detected). / *Self-assessed by Adilsons based on available ingredient data (no animal-derived ingredients detected). / Brand-stated; not certified by an independent body.

Dealing with stubborn dark spots, post-acne marks (PIH), or a dull complexion can be frustrating, especially in a sunny climate like Mauritius where UV exposure is a constant concern. This high-strength serum is designed for those who have tried other brightening products without success and are looking for a potent, fast-acting solution.

• What it is: A highly concentrated serum with 23% pure Vitamin C (L-Ascorbic Acid) to accelerate the fading of hyperpigmentation and boost skin radiance.
• Who it's for: Best suited for normal, combination, and oily skin types already familiar with active ingredients. Not recommended for complete beginners or highly sensitive skin.
• Key Benefits: Visibly fades dark spots and acne scars, brightens overall skin tone, provides powerful antioxidant protection against environmental damage, and helps improve the appearance of fine lines.

1. Cleanse: Start with a clean, dry face.
2. Treat (THIS PRODUCT): Apply 2-3 drops, patting gently until absorbed. See "How to Use" for starting frequency.
3. Protect (AM) or Moisturise (PM): ALWAYS finish with a broad-spectrum sunscreen of SPF 30+ in the morning. At night, follow with a simple moisturiser.

Note: Already own a similar Vitamin C serum? Finish that first to avoid waste and give your skin a fair chance to show results. Substitute, don't stack.

Using Vitamin C in the morning boosts your sunscreen's ability to fight UV damage.

• Minimalist (3 steps): 1) Cleanse → 2) The Vitamin C 23 Serum → 3) Sunscreen (SPF 30+)
• Optional: If your skin feels tight or your sunscreen isn't hydrating enough, you can add a light, hydrating moisturiser before your SPF.
• Wait Times: Wait 1-2 minutes after applying the serum before layering your next product to ensure absorption and prevent pilling.

You can use this serum in the evening, but avoid using it on the same night as other strong actives like retinoids or exfoliating acids (AHA/BHA).

• Minimalist (3 steps): 1) Cleanse (Double-cleanse if you wore makeup or water-resistant sunscreen) → 2) The Vitamin C 23 Serum → 3) Moisturiser
• Texture Rule: Always apply products from the thinnest to the thickest consistency. This watery serum should go on before any creams or oils.

Important: This is a high-concentration product. A patch test and slow introduction are essential to avoid irritation.

• Amount: 2-3 drops for the entire face.
• Method: Apply to clean, dry skin. Gently pat into the skin with your fingertips until absorbed. Start from the center of the face and work outwards.
• Frequency (Ramp-Up Schedule):
  • Week 1-2: Start by using it only 3 times per week (e.g., Monday, Wednesday, Friday) in the evening.
  • Week 3 onwards: If your skin tolerates it well, you can increase to daily use (either AM or PM).
• Photosensitivity Warning: Vitamin C can make your skin more sensitive to the sun. Daily use of a broad-spectrum sunscreen with SPF 30 or higher is mandatory when using this product to protect your skin and see results.
• Watchouts: A slight tingling sensation can be normal upon application. If you experience burning, redness, or a rash, discontinue use. Pilling can occur if you use too much product or don't wait long enough before applying the next layer.
• Safety: For external use only. Avoid contact with eyes. Do not use on broken or irritated skin. Store upright in the refrigerator (3-10°C) to maintain freshness and potency.

To avoid over-exfoliation and irritation, it's best to alternate this powerful serum with other strong actives.

Example Week (AM/PM Focus):

• Mon: AM: Vit C 23 Serum / PM: Hydrating Routine (no strong actives)
• Tue: AM: Hydrating Routine / PM: Exfoliant (AHA/BHA)
• Wed: AM: Vit C 23 Serum / PM: Hydrating Routine
• Thu: AM: Hydrating Routine / PM: Retinoid (if in your routine)
• Fri: AM: Vit C 23 Serum / PM: Hydrating Routine
• Sat/Sun: Focus on hydration and barrier repair. Maybe a soothing mask.

Golden Rule: One strong active per routine. Do not use Vitamin C 23, strong retinoids, and strong exfoliating acids (AHA/BHA) on the same day if you are new to actives.

Mauritius Note: In our strong sun, the antioxidant protection from using Vitamin C in the morning under sunscreen is highly beneficial. Just ensure you are diligent with your SPF application and reapplication.

• Immediate: Skin may feel slightly warm or tingly upon application. You might notice an initial radiant glow. The texture is watery with a slight oily feel that absorbs into a dewy finish.
• 2–4 Weeks: With consistent use, overall skin tone may begin to appear brighter and more luminous. Skin texture can feel smoother.
• 4–8+ Weeks: The visible fading of dark spots, post-acne marks, and sun spots becomes more apparent. Continued use helps protect against new pigmentation and improves skin elasticity. COSRX's brand-led clinical study on 20 subjects showed a 16.26% improvement in visible pigmentation after 4 weeks.

*Brand claim—no public dataset available for independent verification.

Why use a formulated Vitamin C serum, not pure lemon juice?

While lemons contain Vitamin C, applying the juice directly to your skin is a common DIY mistake. Lemon juice is highly acidic (pH ~2) and can cause chemical burns, disrupt your skin's protective barrier, and lead to severe sun sensitivity (phytophotodermatitis), which can ironically cause more dark spots. This COSRX serum is formulated at a precise pH (around 3.0-5.0) for maximum effectiveness and stability, delivering a potent 23% dose of L-Ascorbic Acid in a safe, stabilized base that is much safer and more effective for your skin.

• Works Well With:
  • Hyaluronic Acid & Snail Mucin: Excellent for adding hydration and soothing the skin, which can help buffer the potency of the Vitamin C.
  • Sunscreen: An essential pairing. Vitamin C boosts sunscreen's protective power against UV damage.
  • Vitamin E (Tocopherol): This serum already contains it! They work together to stabilize each other and enhance antioxidant protection.
• Use with Caution:
  • Niacinamide: While they can be beneficial together, applying them back-to-back can sometimes cause flushing in sensitive individuals due to pH differences. To be safe, wait 10-15 minutes between applications or use them at different times of the day (e.g., Vitamin C in AM, Niacinamide in PM).
  • Other Exfoliants (AHA/BHA): Using multiple strong acids in one routine can lead to over-exfoliation and a damaged skin barrier. It's best to alternate them on different days.
• Avoid Using Together:
  • Retinoids (Retinol, Tretinoin): Both are powerful actives that increase cell turnover. Using them in the same routine (e.g., one after the other at night) is too intense for most people and can lead to severe irritation. Alternate nights instead.
  • Benzoyl Peroxide: Can oxidize Vitamin C, making both ingredients less effective. Use at different times of day.

• Ideal For: Oily, Combination, Normal skin types that are not sensitive and are looking for high-potency results.
• Use with Caution:
  • Dry Skin: The high concentration may be drying. Ensure you buffer it with very hydrating products and a rich moisturiser.
  • Acne-Prone Skin: Excellent for fading post-acne marks, but the slightly oily texture and Dimethicone/Palm Oil could be a concern for some. Patch testing is key.
  • Sensitive Skin: This is a very strong product. A 23% concentration of L-Ascorbic Acid will likely be too irritating. We recommend starting with a gentler Vitamin C derivative instead.

• Post-Inflammatory Hyperpigmentation (PIH) / Dark Spots
• Acne Scars (discoloration, not texture)
• Dull & Lifeless Skin
• Uneven Skin Tone
• Sun Spots & Freckles
• First Signs of Aging (Fine Lines & Wrinkles)
• Loss of Elasticity

• Official Korean Name: 더 비타민 씨 23 세럼 (Deo Bitamin C Isipsam Sereom)
• Country of Manufacture: South Korea
• Shelf Life: Use within 2 months after opening (PAO: 2M) due to the instability of pure Vitamin C.
• Date Marks: Check packaging for either a manufacturing date (제조) or an expiration date (까지). Unopened, it is typically good for 24 months from the manufacturing date.
• Authenticity Note: The product has a specially designed cap to control gas generated by the Vitamin C. You may hear a sound when opening it. A dual-layer of liquid (an oil layer on top) is normal and helps maintain freshness; shake gently side-to-side before use.

• Halal Status: Halal-Friendly*. This product does not contain alcohol (ethanol/denat.) or any animal derivatives forbidden in Islam.
• Vegan Status: Vegan-Friendly*. A review of the ingredient list shows no animal-derived components like snail mucin, honey, or carmine.
• Animal Testing Policy: Cruelty-Free. COSRX states they do not test on animals. However, they are owned by AmorePacific, a parent company that is not certified cruelty-free. They do not sell in mainland China where animal testing may be required by law for certain products.

*Self-assessed by Adilsons based on available ingredient data (no ethanol/denat.; no haram animal-derived ingredients detected). / *Self-assessed by Adilsons based on available ingredient data (no animal-derived ingredients detected). / Brand-stated; not certified by an independent body.

• MFDS Class: Functional Cosmetic for Brightening & Wrinkle Improvement.
• Functional Ingredients: Ascorbic Acid, Adenosine.
• Clinical Evidence (Brand-led): COSRX reports clinical results from a 4-week study with 20 subjects, conducted by Dermacosmetic Skin Science Laboratory Co., Ltd. Claims include:
  • 16.26% improvement in pigmentation (visible melasma and blemishes)
  • 32.89% improvement in red skin tone
  • 32.36% improvement in skin radiance (glow)

*Brand claim—no public dataset available for independent verification. / “Brightening” refers to radiance/even tone (e.g., sun spots/PIH); it does not change natural skin color.

Disclaimer: This is a cosmetic product, not a medical treatment. It is not intended to diagnose, treat, cure, or prevent any disease.

Key Actives Explained:

• Ascorbic Acid (23%): The purest and most potent form of Vitamin C. A powerful antioxidant that inhibits melanin production to fade dark spots, boosts collagen synthesis to firm skin, and protects against UV damage.
• Tocotrienol (Super Vitamin E) & Tocopherol: A potent form of Vitamin E that works synergistically with Vitamin C to stabilize the formula and provide enhanced antioxidant protection against environmental stressors.
• Sodium Hyaluronate: A salt form of Hyaluronic Acid that deeply hydrates the skin, helping to plump fine lines and maintain moisture.
• Squalane: A skin-identical emollient that provides lightweight moisture and helps to support the skin barrier without feeling greasy.

Full INCI List:

Water, Ascorbic Acid (23%), Propanediol, Dimethicone, Tromethamine, Ethyl Ascorbyl Ether, Squalane, Caffeine, Sodium Chloride, Sodium Hyaluronate, Sodium Sulfite, Disodium EDTA, Glutathione, Adenosine, Gardenia Florida Fruit Extract, Dextrin, Tocotrienols, Tocopherol, Elaeis Guineensis (Palm) Oil, Butylene Glycol.

Formulated Without: Parabens, Sulfates, Phthalates, Artificial Fragrance.

• Fragrance Status: Fragrance-Free.
• Scent Profile & Intensity: 2/5. This serum has no added perfume, but the high concentration of L-Ascorbic Acid gives it a distinct, sharp, metallic, or sometimes "hot dog water" scent. This is normal for potent, pure Vitamin C products and indicates the product is active.
• EU Allergens: None declared by the brand based on the provided INCI list.

Who should use with caution:

• Individuals with highly sensitive skin, rosacea, or a compromised skin barrier should avoid this high-strength formula.
• If you are new to Vitamin C, start with a lower concentration (5-10%) before trying this product.
• Pregnancy & Breastfeeding: There is insufficient published data on the safety of high-strength (23%) topical Vitamin C during pregnancy or breastfeeding. It is advisable to consult with your doctor before use.

Patch Test Protocol:

1. Apply a pea-sized amount of the serum to a clean, small area of skin, such as behind your ear or on your inner jawline.
2. Wait 24-48 hours. A slight tingle is normal, but if you experience any burning, itching, redness, or rash, wash the area immediately and do not use the product.
3. If no reaction occurs, you can begin incorporating it into your routine slowly as per the "How to Use" guide.

If Irritation Occurs: Stop using the product immediately. Soothe the skin with a simple, fragrance-free barrier cream. If irritation persists, consult a healthcare professional.

• Texture: Very watery and lightweight, with a distinct slip and a slightly oily feel due to the squalane and oil-soluble vitamins.
• Finish: Absorbs quickly, leaving a dewy, radiant finish on the skin.
• Scent: Unfragranced, but has a noticeable metallic or sour smell characteristic of high-concentration L-Ascorbic Acid.
• pH: Approximately 3.0 - 5.0. This low pH is necessary for the stability and penetration of pure Vitamin C.
• Fungal Acne (Malassezia) Compatibility: Contains Dimethicone, Squalane, and Palm Oil, which may be potential triggers for some individuals prone to fungal acne. Patch testing is advised. Individual responses vary.

• "My skin is tingling or feels warm after application." → This is a common and often normal reaction to high-concentration L-Ascorbic Acid due to its low pH. However, if it progresses to a painful burn or causes a rash, stop use immediately.
• "The product is pilling or feels sticky." → You are likely using too much product or not allowing enough time for it to absorb before layering other products. Use only 2-3 drops and wait at least 1-2 minutes.
• "The color of my serum changed to yellow or brown." → This means the Vitamin C has oxidized due to exposure to air, light, or heat. It has lost its potency and should be discarded. This is why refrigeration and using it within 2 months is crucial.
• "I'm not seeing results after 8 weeks." → Ensure you are using a fresh, unoxidized bottle. Most importantly, check your sunscreen habits. Without consistent daily SPF 30+ use, any progress made by the serum will be undone by new sun damage.

• Storage is Key: Our warm, humid climate accelerates the oxidation of pure Vitamin C. It is essential to store this serum upright in the refrigerator to preserve its potency for the recommended 2-month period after opening. Do not store it in a warm bathroom or leave it in a car.
• Humid Summer Use: The lightweight, slightly oily texture might be sufficient as a serum and light hydrator in one for those with oily skin. You may be able to follow directly with sunscreen in the morning.
• Drier Winter / Air-Conditioning: In drier conditions or if you spend a lot of time in AC, you may need to layer a hydrating toner or essence before the serum and a more substantial moisturiser after to prevent dryness.
• Sun Synergy: Given the high UV index in Mauritius year-round, using this serum in the AM provides a critical antioxidant boost to your sunscreen, helping to neutralize free radicals generated by intense sun exposure.

At Adilsons, we guarantee 100% authenticity. This product is sourced directly from COSRX or their authorized distributors in South Korea. Verify your product by checking for the official packaging (KR/EN text mix), batch codes, and seal. If you have any doubts, feel free to contact us on WhatsApp with a photo of your product, and we will assist you.

• Brand Test: COSRX has published results from its own 4-week clinical study on 20 subjects, claiming statistically significant improvements in pigmentation, skin tone, and radiance. As the full dataset is not public, this is considered a brand-led claim.
• Ingredient Rationale: The effectiveness of L-Ascorbic Acid (Vitamin C) at concentrations between 10-20% for stimulating collagen, providing antioxidant protection, and inhibiting melanin production is well-established in independent dermatological research. This serum uses a high 23% concentration to maximize this effect.

While the 20ml bottle seems small, its high concentration means a little goes a long way. However, the key factor is its short shelf life after opening.

• Bottle Size: 20ml
• Dose per Use: ~3 drops (approx. 0.15ml)
• Uses per Bottle: ~133 uses
• Period After Opening (PAO): 2 months (approx. 60 days)

Reorder Cadence: To ensure you are using the product at its peak potency before it oxidizes, you should plan to finish the bottle within 2 months of opening. This means you can use it generously once or even twice daily. Do not try to "save" it for longer, as its effectiveness will decrease significantly.

Starter Essentials (AM Protection)

• ROUND LAB 1025 DOKDO CLEANSER 150ML — A gentle, non-stripping cleanser to create the perfect clean base.
• COSRX The Vitamin C 23 Serum — Your powerhouse antioxidant treatment.
• Beauty of Joseon RELIEF SUN : RICE + PROBIOTICS 50ML — A hydrating, no-white-cast sunscreen to protect your skin and the serum's results.

Soothing & Repair (PM Focus)

• COSRX ADVANCED SNAIL 96 MUCIN POWER ESSENCE 100ML — Apply before the serum to add a layer of hydration and soothing repair, helping to buffer the strong Vitamin C.
• COSRX The Vitamin C 23 Serum — Your targeted brightening treatment.
• SKIN1004 MADAGASCAR CENTELLA SOOTHING CREAM 75ML — A calming, lightweight cream to lock in moisture and support your skin barrier.

Compatibility Note: Avoid using strong acids (AHA/BHA) or retinoids on the same night as this serum.

This high-strength serum is an excellent choice if your primary concerns are stubborn hyperpigmentation and achieving a dramatic brightening effect. However, if your skin has different needs, consider these alternatives from our catalog:

• For More Sensitive Skin (Gentler Vitamin C): Beauty of Joseon LIGHT ON SERUM CENTELLA+VITA C 30ML — Choose this if you're new to Vitamin C or have sensitive skin. It uses a gentler derivative combined with calming Centella Asiatica to brighten without the high risk of irritation.
• For Stubborn Dark Spots & Melasma (Different Actives): Anua NIACINAMIDE 10%+TXA 4% SERUM 30ML — Choose this if your skin doesn't tolerate L-Ascorbic Acid well or if you want to target pigmentation with a different mechanism. The combination of Niacinamide and Tranexamic Acid is highly effective for melasma and PIH.
• For General Brightening & Hydration (Different Texture): AXIS-Y DARK SPOT CORRECTING GLOW SERUM 50ML — Choose this if you prefer a hydrating, gel-like texture. It uses 5% Niacinamide and Squalane to brighten skin and improve tone while providing ample moisture.

Mindful Use: If you already have a comparable Vitamin C or brightening serum at home, we encourage you to finish it first. This helps you avoid waste and get a fair assessment of what that product can do for your skin.

• Packaging: Comes in a 20ml dark brown glass bottle with a separate, sealed dropper to protect the formula from air and light until first use.
• Stability & Storage: This formula is highly unstable due to the 23% pure L-Ascorbic Acid. You must store it upright in the refrigerator (3-10°C) immediately after purchase and keep it there. Keep the cap tightly sealed. Use within 2 months of opening.
• Travel: Due to the need for refrigeration and the potential for leakage if not kept upright, this serum is not ideal for travel.
• Recycling (Mauritius): The glass bottle is recyclable. Please rinse it out and dispose of it in your glass recycling bin. The dropper can be disassembled; the glass part is recyclable, but the plastic and rubber top should be disposed of in the general trash.

(Aggregated sentiment from verified reviews on Reddit, YesStyle, and Amazon within the last 18 months. Experiences are individual.)

• On Fading Dark Spots: "This is one of the strongest Vitamin C serums I've tried, and it works! The 23% ascorbic acid gives a noticeable brightening effect within a few weeks, especially on post-acne marks and uneven tone." - Paraphrased from Harper's Bazaar review (2025-09)
• On Texture & Scent: "The texture is a little heavy/oily but absorbs quickly. There are a few cons... smells awful... and you need to store it in a refrigerator. But this serum is so amazing that I look beyond these cons and use it religiously and the results are amazing." - Amazon customer review (2025-02)
• A Fair Caveat (Sensitivity & Oxidation): "I did try to use them but they stung my face, not sure if it was the product itself or the fact that they were more oxidised than they should be. But after a month, they turned a darker yellow and orangy for sure." - Reddit, r/AsianBeauty (2024-11)

COSRX is a cult-favorite K-beauty brand that takes its name from "Cosmetics" and "RX" (prescription). Their philosophy is rooted in creating effective, ingredient-rich, and skin-friendly products that target specific concerns. With a focus on simple, potent formulations and a commitment to listening to their community, COSRX has become a global go-to for reliable skincare solutions.

• L-Ascorbic Acid (L-AA): The purest, most biologically active form of Vitamin C. It is a powerful antioxidant but is notoriously unstable and can be irritating at high concentrations.
• PIH (Post-Inflammatory Hyperpigmentation): The dark spots or marks left behind after a pimple, wound, or other skin inflammation has healed.
• Antioxidant: A molecule that protects the skin from damage caused by free radicals, which are unstable atoms generated by UV rays, pollution, and other environmental stressors.
• MFDS (Ministry of Food and Drug Safety): The South Korean government agency responsible for regulating cosmetics, ensuring they are safe and meet their functional claims (formerly KFDA).
• PAO (Period After Opening): A symbol on cosmetic packaging that indicates how many months a product will remain stable and safe to use after it has been opened for the first time.

Adilsons

WhatsApp: +230 5 778 2336

Email: info@adilsons.mu

At Adilsons, we are committed to bringing you authentic, effective, and safe K-beauty products. We carefully curate our selection based on evidence, ethics, and suitability for the Mauritian climate. Our promise is one of truth and transparency, ensuring you have the knowledge to make mindful choices for your skin. We guarantee every product is 100% authentic, sourced directly from brands or their authorized channels.

1. Why does the serum sting or feel warm?

A tingling or warming sensation is a common reaction to high-concentration L-Ascorbic Acid due to its very low pH. It's usually temporary. However, if you experience a persistent burn, significant redness, or a rash, you should stop using the product as your skin may be too sensitive for this strength.

2. My serum has turned yellow/orange. Can I still use it?

No. A change in color to yellow, orange, or brown indicates that the Vitamin C has oxidized due to exposure to air, light, or heat. It has lost its antioxidant benefits and may even become pro-oxidant (damaging to the skin). It should be discarded immediately.

3. Why do I have to keep it in the fridge?

Refrigeration slows down the chemical process of oxidation, keeping the pure L-Ascorbic Acid fresh and potent for its intended 2-month lifespan after opening. This is especially important in a warm climate like Mauritius.

4. I have sensitive skin but want to fade dark spots. What should I do?

This 23% serum is likely too strong for you. We recommend starting with a gentler alternative that uses a Vitamin C derivative, such as the Beauty of Joseon Light On Serum, or a product that uses different brightening ingredients like the Anua Niacinamide + TXA serum.

• Best For: Experienced skincare users with resilient skin looking for a powerful, fast-acting treatment to tackle stubborn hyperpigmentation, sun spots, and dullness.
• Key Benefits: High-potency 23% pure Vitamin C for visible results. Provides excellent antioxidant protection to boost sunscreen's effectiveness. Brightens and evens out skin tone significantly with consistent use.
• Keep in Mind: This is a very strong product and can be irritating, especially for sensitive skin. It has a very short shelf life (2 months after opening) and requires constant refrigeration to remain effective. The natural scent can be off-putting to some.

• Coverage: Island-wide delivery (Mauritius).
• Processing & Timing: Orders process in 1–2 business days. Delivery typically takes 1–5 business days after partner pickup.
• Express: May be available. Request on WhatsApp: +230 5 778 2336.
• Liquids/Sensitive Items: Serums like this are eligible for door-to-door delivery or pickup only.
• Returns: No change-of-mind exchanges.
• Refunds (Summary): For items defective/damaged on receipt (report within 48h), wrong item, or manufacturing defect within 6 months. Opened skincare is non-returnable unless damaged on delivery.
• Source of Truth: This is a snapshot. Our official policy pages are the final authority.

Policy Links:

• Refunds & Returns: https://adilsons.mu/policies/refund-policy
• Shipping: https://adilsons.mu/policies/shipping-policy