C-Tetraβ’ Advanced Gel-Serum
C-Tetraβ’ Advanced Gel-Serum
Product Description
A next-generation gel-serum combining 20% stabilized Vitamin C (THDA) with Phyto Exosomes for accelerated brightening, wrinkle smoothing, and powerful antioxidant protection β clinically proven to deliver visible results in just 7 days with zero barrier disruption.
β¨ Texture & Feel
20% Stabilized Vitamin C
Uses THDA (Tetrahexyldecyl Ascorbate), a highly stable, oil-soluble form that penetrates deeper than L-Ascorbic Acid without irritation.
Phyto Exosomes Technology
Plant-derived green tea exosomes deliver proteins, lipids, and messenger molecules to support skin barrier recovery.
Omni-Antioxidant Defense
Acetyl Zingerone enhances Vitamin C benefits while providing superior protection against environmental stressors.
Multi-Weight Hydration
Hyaluronic Acid and Squalane work together to plump, hydrate, and maintain skin softness all day.
π‘οΈ Safety & Compatibility
Topical Vitamin C is generally considered safe. However, Medik8 recommends consulting your physician before use during pregnancy or breastfeeding.
NOT SAFE. Contains Polysorbate 60 and Sorbitan Isostearate which may feed Malassezia yeast. Avoid if you have fungal acne.
Clinically proven to cause 0% barrier disruption. The gentle THDA form is suitable for even reactive skin types.
Can be used alongside Vitamin A products as part of Medik8's CSA Philosophy. Use Vitamin C in AM and Retinol in PM.
π¬ Ingredient Breakdown
π Tetrahexyldecyl Ascorbate (THDA) 20% Proven
A highly stable, oil-soluble form of Vitamin C that penetrates deeper into the skin than L-Ascorbic Acid. Delivers powerful antioxidant protection, stimulates collagen synthesis, and brightens hyperpigmentation without irritation.
- Stability: Remains effective until the last drop β won't oxidize like L-Ascorbic Acid
- Penetration: Oil-soluble structure allows it to penetrate the skin's lipid barrier
- Gentle pH: Works at neutral pH (around 5.0) unlike L-AA which requires low pH of 3.5
π΅ Camellia Sinensis Leaf Vesicles (Phyto Exosomes) Innovative
Plant-derived nano-vesicles from green tea that deliver active compounds directly to skin cells. These exosomes carry proteins, lipids, and messenger molecules that help repair environmental damage and support barrier function.
- Delivery System: Acts as natural carriers to transport actives deep into skin
- Barrier Support: Helps strengthen and restore compromised skin barriers
- Anti-Inflammatory: Green tea polyphenols provide soothing antioxidant benefits
πΏ Acetyl Zingerone Proven
A synthetic antioxidant derived from ginger that provides "omni-antioxidant" protection. It neutralizes multiple types of free radicals and enhances the efficacy of Vitamin C.
- Super Antioxidant: Protects against UV, pollution, and blue light damage
- Synergistic: Amplifies Vitamin C's protective benefits
- Collagen Preservation: Helps prevent breakdown of existing collagen
π§ Sodium Hyaluronate Proven
A low molecular weight form of Hyaluronic Acid that penetrates effectively to deliver deep hydration and plumping benefits.
- Hydration: Holds up to 1000x its weight in water
- Plumping: Reduces the appearance of fine lines instantly
π« Squalane Proven
A skin-identical lipid that mimics the skin's natural sebum. Provides deep moisturization without greasiness while supporting barrier function.
- Biocompatible: Identical to naturally occurring squalene in skin
- Non-Comedogenic: Lightweight, won't clog pores
πΎ N-Acetyl Glucosamine Promising
An amino sugar that helps inhibit melanin production and supports skin cell turnover for brighter, more even-toned skin.
- Brightening: Reduces hyperpigmentation when used consistently
- Exfoliation: Promotes gentle, natural skin renewal
31 ingredients
Aqua (Water), Tetrahexyldecyl Ascorbate, Isododecane, Propanediol, Acetyl Glucosamine, Squalane, Tocopherol, Acetyl Zingerone, Camellia Sinensis (Green Tea) Leaf Vesicles, Hydroxyacetophenone, Sodium Hyaluronate, Cellulose, Avena Sativa (Oat) Kernel Extract, Glycerin, Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer, Citrus Grandis (Grapefruit) Peel Oil, Sucrose Stearate, Tetrasodium Glutamate Diacetate, Ethylhexylglycerin, Acrylates/C10-30 Alkyl Acrylate Crosspolymer, Xanthan Gum, Sodium Benzoate, Cellulose Gum, 1,2-Hexanediol, Polysorbate 60, Sorbitan Isostearate, Citric Acid, Phenoxyethanol, Citral, Linalool, Limonene.
π Where It Fits in Your Routine
Apply in the morning after cleansing and toning. Since this is an emulsion texture, layer it after water-based serums and before oil-based products.
π How to Use
Cleanse & Tone
Start with clean, dry skin. Apply your toner if using one and let it absorb.
Dispense 2-3 Pumps
Press the pump to dispense the gel-serum into your palm. A little goes a long way.
Apply to Face, Neck & DΓ©colletage
Gently massage across your face, neck, and chest area using upward strokes.
Allow to Absorb
Wait 30-60 seconds for the serum to fully absorb before applying moisturizer.
Follow with SPF
Always finish your morning routine with a broad-spectrum SPF30+ sunscreen.
π€ Who Is It For?
β Perfect for you if:
- You want high-strength Vitamin C without irritation
- Dull, uneven skin tone and hyperpigmentation concerns
- Fine lines and early signs of aging
- Sensitive or reactive skin types
- You prefer lightweight, non-greasy textures
- You want visible results within 7 days
- Experienced Vitamin C users ready for higher strength
β Consider alternatives if:
- You have fungal acne (Malassezia folliculitis)
- You're allergic to citrus essential oils
- You prefer fragrance-free products only
- You're on a very tight budget
- You want L-Ascorbic Acid specifically
- You have very dry skin and need rich textures
π― Skin Type Compatibility
Lightweight gel texture absorbs quickly without adding shine. Layers perfectly under sunscreen and makeup.
Squalane provides moisture but may need a richer moisturizer on top. Consider C-Tetra Luxe for more nourishment.
Ideal choice! Balances well across T-zone and cheeks without causing excess oiliness or dryness.
Clinically proven gentle with 0% barrier disruption. THDA is far less irritating than L-Ascorbic Acid.
Low comedogenic rating (1/5). Good for regular acne. NOT suitable for fungal acne due to polysorbates.
20% concentration targets wrinkles, loss of firmness, and age spots. Perfect paired with retinol at night.
π Results Timeline
Instant Radiance & Glow
Skin appears brighter and more luminous immediately after application. Clinically proven to visibly brighten and improve wrinkles in just 7 days.
90% noticed increased radianceImproved Texture & Smoothness
Fine lines appear softened, skin texture becomes more refined, and overall complexion looks healthier and more even.
85% reported smoother skinVisible Brightening & Dark Spot Fading
Hyperpigmentation and dark spots begin to fade noticeably. Skin tone becomes more even and luminous.
80% saw reduced dark spotsFirmer, More Youthful Appearance
Continued collagen support results in improved firmness. Wrinkles appear significantly reduced with consistent use.
75% noticed firmer skinβ Ratings by Platform
βοΈ Pros & Cons
β Praised
- Visible brightening results in just 7 days
- Extremely gentle β 0% barrier disruption
- 20% concentration for maximum efficacy
- Stable THDA won't oxidize like L-AA
- Lightweight, non-greasy gel texture
- Layers beautifully under makeup
- Contains innovative Phyto Exosomes
- Pleasant citrus scent
- B Corp certified, ethical brand
- Pump dispenser preserves freshness
β Criticized
- Premium price point ($79/Β£69)
- Small 30ml bottle size
- Not fungal acne safe
- Contains citrus essential oil (potential sensitizer)
- Not completely fragrance-free
- THDA less researched than L-AA
- May not be enough for very dry skin
- Limited availability in some regions
π° Budget-Friendly Alternatives (Dupes)
Uses L-Ascorbic Acid instead of THDA. More potent but less stable and potentially more irritating. Great value but requires refrigeration.
15% L-Ascorbic Acid with Vitamin E and Ferulic Acid. Smaller 20ml size. More acidic pH may cause tingling on sensitive skin.
Uses a gentler, water-soluble Vitamin C derivative at lower concentration. Very stable but slower results. Great for beginners.
15% Ethyl Ascorbic Acid β stable, effective, and affordable. Lacks the advanced Phyto Exosome technology but delivers good brightening results.
π Comparison with Competitors
Medik8 C-Tetra Advanced (This Product)
$79SkinCeuticals C E Ferulic
$182Paula's Choice 25% Vitamin C + Glutathione
$59Revision Skincare C+ Correcting Complex 30%
$176π¦ Storage & Shelf Life
6 months after opening. THDA is stable but use within 6 months for optimal potency.
Store in a cool, dry place away from direct sunlight. Refrigeration not required but can extend freshness.
Dark glass bottle with airless pump dispenser to minimize oxidation and preserve potency.
Yes, 30ml is under 100ml liquid limit. Glass bottle β wrap carefully to prevent breakage.
β Frequently Asked Questions
Topical Vitamin C (including THDA) is generally considered safe during pregnancy and breastfeeding. However, Medik8 recommends consulting your physician or midwife before use as they cannot provide medical advice. The product does not contain retinoids, salicylic acid, or other ingredients typically advised to avoid during pregnancy.
No, this product is NOT safe for fungal acne. It contains Polysorbate 60 and Sorbitan Isostearate, which are esters that can feed Malassezia yeast and potentially worsen fungal acne. If you have Malassezia folliculitis, look for a Vitamin C serum without polysorbates or esters.
Yes! Medik8 actually recommends this as part of their CSA Philosophy. Use C-Tetra Advanced in the morning with sunscreen, and use your retinol/Vitamin A product at night. This combination maximizes anti-aging benefits while minimizing irritation. You don't need to alternate days.
Yes, but layer carefully. Since THDA works at a neutral pH (unlike L-Ascorbic Acid), it's more compatible with acids. Apply water-based acids first, wait for absorption, then apply C-Tetra Advanced. Alternatively, use acids at night and Vitamin C in the morning.
C-Tetra Advanced is excellent for combination, oily, sensitive, and mature skin types. The lightweight gel texture is particularly suited for those who find oily serums too heavy. It's clinically proven gentle on sensitive skin with 0% barrier disruption. Dry skin types may prefer C-Tetra Luxe which is more nourishing.
Clinical studies show visible brightening and wrinkle improvement in just 7 days. Most users notice an instant glow immediately after application. For significant dark spot fading and anti-aging benefits, consistent use for 4-8 weeks is recommended. Full collagen-building benefits typically appear after 8-12 weeks of daily use.
Apply in the morning after cleansing and toning, but before moisturizer and sunscreen. Since C-Tetra Advanced is an emulsion (thicker texture), layer it after water-based serums (like hyaluronic acid) and before oil-based products. Always finish with SPF30+ sunscreen.
C-Tetra Advanced has a low comedogenic rating of 1/5. The main potential pore-clogger is Squalane, but it's generally well-tolerated and is similar to your skin's natural sebum. Most users, including those with oily and acne-prone skin, do not experience breakouts. However, everyone's skin is different β patch test first if you're concerned.
Use within 6 months after opening for optimal results. THDA is much more stable than L-Ascorbic Acid and won't turn orange/brown like traditional Vitamin C serums. The dark glass bottle and pump dispenser help preserve the formula. Store in a cool, dry place away from direct sunlight.
C-Tetra (7% THDA): Original formula, lightweight oil texture, ideal for Vitamin C beginners and sensitive skin. C-Tetra Luxe (14% THDA): Richer oil-serum with red ginseng, Vitamin E, and nourishing oils β best for dry/mature skin. C-Tetra Advanced (20% THDA): Highest strength, gel-serum texture with Phyto Exosomes β best for experienced users wanting maximum brightening with lightweight feel.
Verdict: Medik8 C-Tetra Advanced delivers on its promises of gentle yet powerful brightening. The 20% THDA concentration provides clinical-strength Vitamin C without the irritation of L-Ascorbic Acid, while innovative Phyto Exosomes support barrier health. Clinically proven results in 7 days make this an impressive choice for anyone seeking a high-performance Vitamin C serum. The only drawbacks are the premium price point and unsuitability for fungal acne. If you want maximum efficacy without compromise, this is worth the investment.
Product Overview
What are Quick Product Notes?
Quick product notes are a great way to check if a product is free from commonly avoided ingredients by skincare enthusiasts. These preferences come about for different reasons depending on the ingredient such as personal experiences, sensitivities, health preferences & etc.
Pro Tip Alert!
Just because a product is not free from a common preference does not mean it's a bad product! You can make a personal decision whether or not you want to use a product that contains these ingredients or not - click the labels of the preference to read more about them.
Quick Product Notes
Paraben-Free
Paraben-Free
Understanding Parabens
Parabens are a large group of preservatives which are used to prevent bacteria growing in cosmetic formulations. There has been some healthy controversy surrounding them due to a few studies finding paraben presence in breast tumours and breast tissue. However, the majority of the scientific community have deemed these findings non-conclusive due to the limitations of these studies. There's still a lot of support for avoiding parabens following the better safe than sorry route. If you do we completely support you! If you are concerned about the health safety of parabens, then feel free to avoid them by looking out for the Paraben-Free icon. If not, don't worry about it - they do have had one of the longest safety records as preservatives!
Which Ingredients are classified as Paraben?
A product will be paraben-free if it does not contain any of the following parabens:
- Sodium Isobutylparaben
- Sodium Ethylparaben
- Sodium Butylparaben
- Propylparaben
- Isopropylparaben
- Isobutylparaben
- Sodium Propylparaben
- Butylparaben
- Ethylparaben
- Sodium Methylparaben
- Methylparaben
Sulfate-Free
Sulfate-Free
Understanding Sulfates
Sulfates are a large group of ingredients which act as cleansing agents in Cosmetics. They help loosen up the dirt and grime from your skin and hair to allow for water to wash it away with ease. However some sulfates are so good at their job, they can wash off your skinβs own natural oils that keep it moisturised and protected which can lead to dryness and irritation. Most people will find no issues with sulfate, however if you find your skin doesn't like sulfates then free feel to avoid them by looking out for the sulfate-free icon on Skincarisma.
Which ingredients are classified as sulfates?
We've taken the Sulfates which are considered more harsh for our Sulfate-Free status. A product will be Sulfate-Free if it does not contain any of the following Sulfates:
- TEA-Dodecylbenzenesulfonate
- Ammonium Laureth Sulfate
- Sodium Lauryl Sulfate
- PEG-15 Cocamine
- Sodium Laureth Sulfate
- Sodium Cocoyl Sarcosinate
- Sodium C14-16 Olefin Sulfonate
- Dioctyl Sodium Sulfosuccinate
- Ammonium Xylenesulfonate
- Ammonium Lauryl Sulfate
- Sodium Xylenesulfonate
- Sodium Myreth Sulfate
- Sodium Lauryl Sulfoacetate
Alcohol-Free
Alcohol-Free
Understanding Simple Alcohols
Alcohol ingredients are widely used in cosmetics and come in different types. For the most part alcohols are not problematic at all. However one type of alcohols, simple alcohols can be quite drying to the skin because it evaporates very quickly. This can cause irritation which can also lead to other skin complications. These alcohols should never be used alone on your skin, but combined with other cosmetic ingredients, they are normally without issue. However, for some people with sensitive and easily irritable skin, avoiding products with these simple alcohols may be beneficial. If you find your skin doesn't like these simple alcohols, then free feel to avoid them by looking out for the Alcohol-Free icon.
Which Ingredients are classified as Alcohol?
A product will be alcohol-free if it does not contain any of the following alcohol ingredients:
- SD Alcohol
- Alcohol Denat
- Isopropyl Alcohol
- Alcohol
Silicone-Free
Silicone-Free
Understanding Silicones
If you've ever used a skincare, makeup or beauty product that's made your skin look and feel smoother tempoarily - it's likely contained Silicone. They are a popular class of ingredients found in cosmetics due to their smooth, soft, easy-to-spread and smooth properties that help creates an artificial layer/barrier on top of skin or hair (commonly found in conditioners).
For the same reasons they are popularly used, they are also commonly avoided. Anecdotally, many individuals have reported that Silicones cause/excerbate breakouts, irritation, cause a feeling of skin being unable to breathe, cause clumping of cosmetic products and find it difficult to wash off. As a result, those who find them problematic are avoiding them and increasingly, cosmetic companies are avoiding them as well.
If you have had bad experiences with Silicones in the past, or suspect they are problematic then look out for the tick on the Silicone-free label.
Disclaimer
The Silicone-free label only includes the most common Silicone ingredients that have indentified been reported by individuals that could potentially cause issues.
These include: Amodimethicone, Behenoxy Dimethicone, Bis-Aminopropyl Dimethicone, Cetearyl Methicone, Cetyl Dimethicone, Cyclomethicone, Cyclopentasiloxane, Dimethicone, Dimethicone Copolyol, Dimethiconol, Methicone, Phenyl Trimethicone, Phenyl Trimethicone, Stearoxy Dimethicone, Stearyl Dimethicone, Trimethylsilylamodimethicone.
Note, that this does not include all ingredients part of the Silicone class of ingredients.
EU Allergen-Free
EU Allergen-Free
Understanding the Identified Contact Allergens
The EU's Scientific Committee on Consumer Safety (SCCS) has identified and established 26 cosmetic ingredients that are likely contact allergens (potential to cause skin allergies) as demonstrated in clinical or epidemiological studies. The EU's SCCS have recommend cosmetic companies to disclose them on the labels if used and in cases where the concentration exceeds 0.001% in leave-on products and 0.01% in rinse-off products, then they must be labelled.
Look out for the tick on the EU-Allergen free label to know your cosmetic is free from any of the 26 identified cosmetic ingredients.
For more information regarding the EU's Scientific Committee on Consumer Safety, please visit their official website.
Disclaimer
The EU Allergen Free label is for the 26 ingredients identified by the EU SCCS and products will be only flagged if a suspected ingredient is on it's ingredient list. It is possible for cosmetics to contain one of the suspect ingredients without it appearing on the ingredient list due to it not reaching the concentration threshold to disclose it and cosmetic manufacturers choice to not disclose it.
Also note, the EU Allergen Free label is not personalized for your own allergies you may have and it does not constitute as medical advice. For your specific case, always consult your medical professiona such as dermatologist, physician, pharmacist, or health care provider - please read our medical disclaimer for more information.
Fungal Acne (Molassezia) Safe
Fungal Acne (Molassezia) Safe
Understanding Fungal Acne (Pityrosporum Folliculitis/Malassezia Folliculitis)
Pityrosporum Folliculitis/Malassezia folliculitis or simply known as Fungal Acne is a persistent acne-like condition that commonly responds poorly to traditional acne-treating methods. Unlike most cases of Acne where bacteria is the culprit, Fungi is the culprit of Fungal Acne (Hence the name!). There are certain classes & groups of ingredients that have been shown to promote and feed the growth of the Fungal Acne, Fungi such as fatty acids, oils, esters, polysorbates and fermented ingredients.
For more information regarding Fungal Acne, please visit Simple Skincare Science (f.c) - #3 of our Recommend Skincare Resources for an amazing comprehensive guide!
Please Read: How to use the Fungal Acne (Malassezia) Label
At SkinCarisma, we've done our best to identify as many ingredients as possible but note the fungal-free label may not be 100% accurate due to the complexconditions and combination of ingredients that malezzeria can thrive on.
Additionally, products that may contain ingredients that have shown to feed Malassezia may not neccessarily exacerbate the condition due to concentration of ingredient used in the product, this information is simply not available on the products.
As a result, please note this is only an experimental label that can be best used to possible identify problematic products you have used in the past. It is in no way a perfect identifier nor a predictor in whether or not it will exacerbate or cause fungal acne. It will continue to be worked on as more information and research comes to light.
If you find any ingredients you believe should be included, please email us at snails@skincarisma.com.
Disclaimer
Due to the lack of substantial research into this area it is very likely there are other ingredients and class/groups of ingredients that could feed Fungal Acne which have not been indentified.
The Fungal-Safe label does not constitute as medical advice. For your specific case, always consult your medical professiona such as dermatologist, physician, pharmacist, or health care provider - please read our medical disclaimer for more information.
What are Notable Effects & Ingredients?
Ever used a product that promised a certain effect but provided no results? It might not have contained any notable ingredients that could have been responsible for that promised effect. It doesn't matter what the marketing or packaging Β«promisesΒ» it can do, if it doesn't contain anything that can help - then the likelihood of it helping is low.
We help you identify key notable ingredients that have been shown to help with effects such as acne-fighting, brightening, UV-protection, wound healing & anti-aging to help you achieve your skincare goals smarter. Please note that different notable ingredients have varying levels of research behind them, some are extremely well proven yet some have mixed research in their efficacy.
Pro Tip Alert!
Just because a product doesn't contain any notable ingredients doesn't mean it's bad. And a product with notable ingredients (or even many) doesn't necessarily guarantee the efficacy of the product performing these effects either. There are other factors such as ingredient quality, concentration and formulation that will ultimately determine this.
Be smart and use this as just a starting point for you to make more informed and smarter choices and compare it with reviews to see if the product is right for you
Notable Effects & Ingredients
Anti-Aging from 4 ingredient(s):
Brightening from 4 ingredient(s):
Promotes Wound Healing from 4 ingredient(s):
What are Ingredients Related to Skin Type?
Why are some products great for some people and horrible for others? Well everyone has different skin types and different reactions to the same ingredients.
We've identified a range of ingredients that are commonly regarded as potentially good or bad for those with Dry, Oily/Acne-Prone or Sensitive skin.
Pro Tip Alert!
A product that contains good or bad ingredients for your skin type doesn't always flat out make the entire product good or bad for your skin. There are other factors such as ingredient quality, concentration and formulation that will ultimately determine your skins reaction.
One of the best ways to use this section is to troubleshoot products you've had bad experiences with in the past. Check if it contains any of the marked ingredients to point out suspect ingredients to avoid in the future!
Ingredients Related to Skin Types
Dry Skin
Oily/Acne-Prone Skin
Sensitive Skin
What is the Ingredient Safety Breakdown?
Ingredient Safety Breakdown refers to the percentage % of ingredients in different risk categories as classified by EWG (Environment Working Group) if they are available. There are almost endless cosmetic ingredients and they are one of the few organisations globally that have assigned ratings to a lot of the more commonly used ingredients which is why we reference them.
Pro Tip Alert!
EWG is seen by many to be more on the alarmist side in their assignment of health ratings resulting in rating ingredients as riskier than they actually are. We recommend using this a reference point rather than a strict guide of ingredient safety and to always do further research if into ingredients that you may find suspect.
Ingredient Safety Breakdown
Product ingredient list
| EWG | CIR | Ingredient Name & Cosmetic Functions | Notes |
|---|---|---|---|
| 1 |
Water
Solvent, Skin Conditioning
|
|
|
| 1 |
Tetrahexyldecyl Ascorbate
Skin Conditioning, Antioxidant
|
Brightening
Anti-Aging
Redness
Texture
Pores
|
|
| 1 |
Isododecane
Solvent, Perfuming, Emollient, Fragrance
|
|
|
| 1 |
Propanediol
Solvent, Viscosity Controlling, Viscosity Decreasing Agent
|
|
|
| 1 |
Acetyl Glucosamine
Skin Conditioning
|
Brightening
|