C-Tetraβ’ Advanced Gel-Serum
C-Tetraβ’ Advanced Gel-Serum
Product Description
Medik8 C-Tetraβ’ Advanced is a lightweight, fast-absorbing gel-serum powered by 20% stabilised vitamin C (tetrahexyldecyl ascorbate). Reinforced with green tea phyto exosomes and the omni-antioxidant acetyl zingerone, it visibly brightens, smooths fine lines and shields skin from daily pollution β all without the sting or oxidation drama of traditional L-ascorbic acid. Clinically shown to brighten and improve the look of wrinkles in just 7 days with 0% barrier disruption.
β¨ Texture & Feel
20% Stabilised Vitamin C
A high 20% dose of tetrahexyldecyl ascorbate β an oil-soluble vitamin C that penetrates deeply for brightening without the irritation of L-ascorbic acid.
Phyto Exosome Technology
Green tea derived messenger molecules help shield skin and support its natural recovery from environmental stress and pollution.
Acetyl Zingerone Defence
An "omni-antioxidant" derived from ginger that stays stable in sunlight and disrupts multiple types of UV-triggered free-radical damage.
7-Day Visible Results
Independently clinically tested over 4 weeks on 32 participants β brighter, smoother-looking skin in 7 days with 0% barrier disruption.
π‘οΈ Safety & Compatibility
Contains no retinoids, hydroquinone or chemical sunscreen. Vitamin C derivatives are generally considered safe β always confirm with your doctor.
Not malassezia-safe. Contains polysorbate 60, sorbitan isostearate, sucrose stearate and squalane which may feed malassezia.
Naturally scented with grapefruit peel oil, so it contains citral, linalool and limonene. Patch test if you have reactive skin.
Pairs well with niacinamide, peptides, HA and SPF. Best used AM; keep retinoids and strong acids for your PM routine.
THD vitamin C works at skin's natural pH, so it's far gentler than acidic L-ascorbic acid serums β a popular pick for sensitive types.
No harsh alcohols, no parabens, no silicones and no sulfates. Vegan and cruelty-free formula.
π¬ Ingredient Breakdown
π Tetrahexyldecyl Ascorbate (THD Vitamin C) 20% Proven
A stable, oil-soluble form of vitamin C and the star of this serum. Because it's lipid-soluble, it penetrates deeper into the skin's fatty layers than traditional ascorbic acid while delivering the same antioxidant, brightening and collagen-supporting benefits β without needing a low, irritating pH.
- Source: Concentrations of 5%+ are used to fade dark spots and hyperpigmentation; 20% targets maximum brightness.
- Source: Even at 0.1% THD shows antioxidant activity; it works at skin-neutral pH, making it ideal for sensitive skin.
𧬠Green Tea Phyto Exosomes Complex Promising
Plant-derived messenger molecules (from Camellia Sinensis) that deliver proteins, lipids and signalling molecules to skin cells, helping support the skin's natural repair processes and barrier while improving the controlled delivery of the vitamin C.
- Source: Green tea polyphenols are strong antioxidants that neutralise UV-triggered free radicals and soothe inflammation.
π« Acetyl Zingerone Antioxidant Promising
An "omni-antioxidant" derived from ginger that remains stable in sunlight. It's able to fight multiple types of free-radical damage and disrupt the UV-damaging processes that drive premature ageing and dullness.
- Source: Stays stable in sun and helps interrupt UV-induced oxidative stress on the skin.
π§ Sodium Hyaluronate (Hyaluronic Acid) Humectant Proven
The salt form of hyaluronic acid and a powerful humectant. It holds water in the skin to deliver lightweight hydration and a plumped, refreshed look β which is why the serum feels hydrating rather than drying despite the high active percentage.
- Source: Naturally found in the body; excels at binding water to hydrate and plump skin.
π§ͺ Acetyl Glucosamine (NAG) Booster Proven
An amino-acid sugar naturally found in skin. It helps boost the skin's own hyaluronic acid production for added hydration, and provides antioxidant protection. Paired with brighteners, it's shown to help reduce the look of discolouration.
- Source: Shown to be effective at reducing the appearance of discolouration when paired with niacinamide.
πΏ Squalane Emollient Proven
A skin-identical emollient that helps the skin hold onto moisture and softens texture. It's non-irritating even at 100% concentration and gives the gel-serum its smooth, fast-absorbing slip without a heavy or greasy feel.
- Source: Research shows squalane is non-irritating even at 100% and suits sensitive skin.
31 ingredients
Water, Tetrahexyldecyl Ascorbate, Isododecane, Propanediol, Acetyl Glucosamine, Squalane, Tocopherol, Acetyl Zingerone, Camellia Sinensis Leaf, Hydroxyacetophenone, Sodium Hyaluronate, Cellulose, Avena Sativa Kernel Extract, Glycerin, Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer, Citrus Grandis 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
Use in the morning on cleansed skin, before heavier creams. Always finish with a broad-spectrum SPF β vitamin C and sunscreen are a proven daytime duo.
π How to Use
Cleanse
Start with clean, dry skin in the morning after your usual cleanser.
Apply 2-3 Pumps
Massage 2-3 pumps across the face, neck and dΓ©colletage. A little goes a long way.
Moisturise
Follow with your moisturiser to lock in hydration once the serum has absorbed.
Protect with SPF
Always finish your morning routine with a broad-spectrum sunscreen.
Patch Test First
New to vitamin C? Patch test 24 hours before first use and introduce gradually.
π€ Who Is It For?
β Perfect for you if:
- You want visible brightening and a more even skin tone
- You have sensitive skin that stings with traditional vitamin C
- You prefer a lightweight, fast-absorbing gel over an oily serum
- You're targeting fine lines, dullness and pollution damage
- You want a higher-strength (20%) but gentle vitamin C
β Consider alternatives if:
- You're managing fungal acne / malassezia (not FA-safe)
- You react to fragrance allergens like limonene or linalool
- You want a fully fragrance-free formulation
- You're on a tight budget (this is a premium-priced serum)
- You specifically want classic L-ascorbic acid + ferulic acid
π― Skin Type Compatibility
Lightweight gel-serum absorbs fast and leaves a dewy, non-greasy finish.
HA and squalane add hydration, but very dry skin will want a richer moisturiser on top.
Balances hydration and brightening across all zones without heaviness.
Gentle THD vitamin C suits sensitive skin, but citrus fragrance means a patch test is wise.
Low comedogenicity (1/5), but it is not fungal-acne safe if you struggle with malassezia.
π Results Timeline
Instant Refresh
Skin feels hydrated, smooth and instantly looks fresher and more luminous after first use.
Immediate glowVisible Brightening
Clinically shown to brighten skin and visibly improve the look of wrinkles within one week, with 0% barrier disruption.
Clinically proven in 7 daysEven Tone & Smoothness
Continued daily use over the 4-week study period builds on radiance, with a smoother, more even-looking complexion.
Study period: 4 weeksLong-Term Defence
Sustained antioxidant protection helps defend against pollution and free radicals that drive premature ageing.
Best with daily AM useβ Ratings by Platform
βοΈ Pros & Cons
β Praised
- Absorbs beautifully β not greasy, no pilling under makeup
- Gentle even for those who can't tolerate other vitamin C serums
- Visible brightening and glow, often within days
- Pleasant fresh-orange scent that many users love
- High 20% active strength with 0% barrier disruption
- Vegan, cruelty-free and reef-safe formula
β Criticized
- Premium price point (around $77 / Β£69 for 30ml)
- Contains fragrance allergens (citral, linalool, limonene)
- Not suitable for fungal-acne / malassezia-prone skin
- Citrus scent can be too much for fragrance-averse users
- Small 30ml size relative to the cost
π° Budget-Friendly Alternatives (Dupes)
Uses the same family of oil-soluble vitamin C ester (THD-type) at 20% in a vitamin F (fatty acid) base. Far cheaper, but a much simpler formula without exosomes, HA or acetyl zingerone, and an oilier texture.
A fragrance-free THD ascorbate serum with ceramides aimed at sensitive skin. Lower active strength and less luxurious feel, but a strong, affordable, allergen-free alternative.
A multi-form vitamin C serum with a lightweight, beginner-friendly feel and brightening focus. Different vitamin C blend and lower potency than the 20% THD here, but accessible and gentle.
π Comparison with Competitors
Medik8 C-Tetra Advanced (Featured)
~$77SkinCeuticals C E Ferulic
~$182Paula's Choice C25 Super Booster
~$58The Ordinary Ascorbyl Tetraisopalmitate 20%
~$18π¦ Storage & Shelf Life
6 months after opening β vitamin C degrades over time, so use it up while it's fresh.
Store in a cool, dry place away from direct sunlight and heat above 45Β°C / 113Β°F.
Opaque pump bottle that limits light and air exposure to protect the vitamin C.
Yes β 30ml is well under the 100ml cabin liquid limit for carry-on.
β Frequently Asked Questions
The formula contains no retinoids, salicylic acid, hydroquinone or chemical sunscreen filters, and vitamin C derivatives like THD ascorbate are generally considered safe during pregnancy and breastfeeding. The main thing to be aware of is the citrus-derived fragrance allergens. As always, we recommend confirming with your doctor or midwife before adding any active to your routine while pregnant or nursing.
No. The serum contains several ingredients that can feed malassezia, including polysorbate 60, sorbitan isostearate, sucrose stearate and squalane (depending on its source). If you are actively managing fungal acne, this is not the best choice β a stripped-back, ester-free vitamin C would be safer.
It already is your vitamin C step, so there's no need to add another. It layers well with niacinamide, peptides, hyaluronic acid and SPF in the morning. Keep retinol and strong AHA/BHA exfoliants for your evening routine to avoid over-stressing the skin and using both in the same application.
It's excellent for oily and combination skin thanks to its lightweight, fast-absorbing gel texture, and good for dry and sensitive skin too β the gentle THD vitamin C works at skin's natural pH. The main exception is fungal-acne-prone skin, where it scores only moderately because the formula is not malassezia-safe.
Skin can look instantly refreshed and more radiant from the first use. In an independent clinical study over 4 weeks on 32 participants, the serum was shown to brighten skin and visibly improve the look of wrinkles in just 7 days, with 0% barrier disruption. Continued daily morning use builds on these results over 4 to 12 weeks.
Use it in the morning after cleansing (and toning, if you tone), before your moisturiser. Massage 2-3 pumps across the face, neck and dΓ©colletage, let it absorb, then follow with moisturiser and always finish with a broad-spectrum sunscreen.
It has a low comedogenic rating of around 1 out of 5. The key emollients β squalane and isododecane β are low on the pore-clogging scale, and the gel-serum is designed to absorb quickly without a heavy, greasy film. Most users, including those with oily and combination skin, find it doesn't clog pores.
Around 6 months after opening (6M PAO). Because vitamin C degrades with exposure to light, air and heat, use it within that window and store it in a cool, dry place out of direct sunlight to keep it at full strength.
Verdict: Medik8 C-Tetra Advanced is a smart, high-performance vitamin C serum that delivers serious 20% brightening power in a remarkably gentle, lightweight gel. The clever combination of stabilised THD vitamin C, green tea phyto exosomes and acetyl zingerone means real antioxidant defence without the sting, oxidation or barrier disruption of classic L-ascorbic acid serums β making it a standout for sensitive and combination skin. The premium price, citrus fragrance allergens and lack of fungal-acne safety are the main trade-offs. If you want an effective, sensitive-skin-friendly vitamin C and don't mind paying for it, this is one of the best gel-serum options on the market.
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
|