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Best Vitamin C Serum: Dermatologist Explains The Ideal Formulation For Sensitive Skin

May 13, 2023
Best Vitamin C Serum Characteristics

Are you searching for the best vitamin C serum formulation for your skin type? Which vitamin C serum do dermatologists recommend? The ideal formulation follows certain criteria which we will go through in this article. 

We will begin with the science behind how a vitamin C serum works.

@drteowanlin Which vitamin C serum do dermatologists recommend? Are you searching for the best vitamin C serum formulation for your skin type? What’s in the ideal vitamin C serum? We will begin with the science behind how a vitamin C serum works. It is important to include synergistic actives such as Botanicals Humectants i.e. sodium hyaluronate Full guide 👆🏻 #vitamincserum #sgtoktok #sgdoctor #dermatologist #tiktoksg🇸🇬 #skincareroutine #skincaretips #skincare101 #skincareproduct ♬ original sound – Dermatologist Dr.TWL

The Science Behind The Best Vitamin C Serum Formulation


L-ascorbic acid is the active molecule from raw vitamin C which works on skin. It is also highly unstable, meaning it gets oxidised rapidly upon exposure to environmental oxygen. Once it is oxidised, it is rendered useless. By default, all vitamin C serums are packaged in an amber glass bottle to minimise oxidation by light as well. The best vitamin C serum formulations get around this problem by:

  • Increasing the concentration of L-ascorbic acid to ensure there is still a sufficient amount that works on skin taking into account the oxidation process 
  • Ensuring the companion ingredients have anti-oxidant properties i.e. green tea extracts can synergise and boost the effectiveness of L-ascorbic acid
  • Instead of L-ascorbic acid, vitamin C can be formulated as a salt known as sodium ascorbyl phosphate (SAP) which is highly stable and resistant to oxidation

In the case of sodium ascorbyl phosphate (SAP), its functional form is still L-ascorbic acid. It is absorbed via the epidermis and when it reaches the dermis, the enzyme phosphatase transforms it to L-ascorbic acid in a one-step conversion. There is hence no atmospheric related oxidation and the effectiveness is preserved. Clever, isn’t it?

L-Ascorbic Acid vs Sodium Ascorbyl Phosphate


The concentration of L-ascorbic acid does matter. When L-ascorbic acid is chosen as the active vitamin C compound, concentrations generally are at 20% to take into account environmental loss. However, this also means that the formulation becomes acidic and can irritate sensitive skin. For SAP on the other hand, concentrations at 4-5% are sufficient because there is minimal to no risk of oxidation as it is a stable salt. In fact, concentrations of just 1% have been shown to inhibit the acne-causing bacteria, cutibacterium acnes. 

@drteowanlin When will my skin stop purging? I answer your acne purging questions in this video tutorial. For more get my skincare blueprint 👆🏻 How to treat purging skin Skin purging process How to stop skin purging Skin purging vs breaking out Dealing with purging Acne purging phase acne purging cause acne purging experience acne purging should heal acne after purging tretinoin results What does purging look like #acnepurging #acnetreatment #acneskin #tiktoksg🇸🇬 #sgtiktok #sgdoctor #learningisfun #learnontiktok #dermatologist ♬ original sound – Dermatologist Dr.TWL

Acne purging can be a nightmare—it’s also a myth that acne treatments cause purging. It occurs mainly with retinoid treatment. Microcomedones form under the surface of skin 2-4 weeks before they appear, and retinoid therapy drives the comedones to the surface. The beneficial effects occur when it increases skin cell turnover, so there is less follicular plugging.

But here’s the problem. Retinoids are also pro-inflammatory.  Which means it causes acne flare-ups. Before it even gets to work, we see the side effects first. But here’s a secret—certain botanicals can treat acne without the purging side effect. Berberine for example treats acne by suppressing inflammation and comedone formation. It also regulates sebum production and reduces post-inflammation hyperpigmentation which means your scars heal faster. 


This refers to the sensitising potential of vitamin C. As an acidic compound, it can irritate skin when concentrations are too high especially when applied to sensitive skin types. This is why vitamin C serums should not be applied to areas of active eczema, raw or broken skin. The exception is with acne bumps and cysts, as vitamin C itself creates a beneficial antioxidant environment that prevents acne bacteria from proliferating.

Vitamin C also prevents the oxidation of sebum, which contributes to comedone formation. However, when sodium ascorbyl phosphate is used, there is minimal to no risk of irritation. This is because it is a stable salt and the concentrations used are lower. Unlike L-ascorbic acid, there is no need to take into account environmental oxidation.


What’s in the ideal vitamin C serum? 

It is important to include synergistic actives such as 

  • Botanicals 

Certain botanical extracts have an anti-inflammatory effect on skin. For instance our pharmacy’s formulation contains camellia sinesis, sage extract, brassica and belamcanda chinesis root extracts which also create a profound antioxidant environment to enhance the efficacy of the product.  

Best Vitamin C Serum Dermatologist Recommended

We know the importance of an intact skin barrier—a damaged skin barrier leads to conditions like eczema and dermatitis. But did you know the skin barrier is also a barrier to absorption? This is why dermatologists are concerned with enhancing transdermal absorption, which refers to the ability of cosmeceuticals to cross the skin barrier into the deeper layers of skin such as the dermis where it exerts its effects on target cells. 

  • Humectants i.e. sodium hyaluronate
  • Occlusives i.e. castor oil 

Hyaluronic acid is a well known humectant, which means it traps water under the skin. It is a hygroscopic molecule which means it attracts water and in fact is known to hold 1000 times its own weight in moisture levels. The ideal vitamin C serum formula should contain a humectant which can also be polyglutamic acid or glycerin as this enhances the effects of vitamin C on skin—by creating a moist environment it increases epidermal permeability. This enhances absorption of vitamin C via the skin barrier. Plant-derived oils like castor also facilitate transdermal absorption by increasing the overall occlusivity of the product. 

@drteowanlin How the Vita C Gold Serum by Dr.TWL Pharmacy is formulated as the gold standard in the anti-ageing antioxidant family In this section, I’ll explain why topical vitamin C is considered a key antioxidant in skincare formulations as well as benefits on skin physiology. You will learn how to choose the best vitamin C serum for your skin type and also how to incorporate it into your day and night skincare routine. Get the full tutorial👆🏻 #vitamincserum #sgtoktok #sgdoctor #dermatologist #tiktoksg🇸🇬 #skincareroutine #skincaretips #skincare101 #skincareproduct #brighteningserum #skinbrighteningproducts #skinbrighting ♬ original sound – Dr.TWL Dermatologist

You may have heard of wet wrap therapy which refers to using layers of wet fabric on top of moisturisers to enhance absorption of skincare. Sheet masking is a concept based on this technique as well. But did you know that when formulating skincare, ingredients can also be paired in order to boost its effectiveness? For instance, vitamin C paired with humectants and occlusives can be better absorbed via the epidermis. When paired with botanicals, it can enhance the overall anti-oxidant and anti-inflammatory effects on skin. For acne prone skin ingredient pairing can also help regulate sebum production. 

  • Natural moisturising factors i.e. amino acids methionine
  • Peptides
Barrier Repair Speed Guide
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    How Vitamin C Can Be Used to Treat Acne Purging 

    Vitamin C serums are underrated, especially when it comes to treatment of acne. I generally don’t recommend application of vitamin C serums on areas of raw or broken skin—but the exception really is with inflamed acne bumps and cysts. Here are the reasons why. 

    Inflammation Related to Sebum Oxidation

    Firstly, the type of inflammation in acne is slightly different from what occurs in eczema or areas of injury. It’s inflammation that’s driven by an oxidative process, namely from oxidation of sebum. Acne prone skin tends to produce excess oil, and this isn’t just uncomfortable. It’s actually driving the inflammation which makes acne flare-ups worse. 

    Vitamin C Serum Benefits UV Protection, Anti-Inflammatory, Sebum Control

    Infection/Colonisation with C. Acnes

    Acne is also associated with bacteria—in particular Cutibacterium acnes. Vitamin C serums create an anti-oxidant environment which inhibits the growth of this bacteria. This means vitamin C serums can be used for acne prevention and long term maintenance treatment as well.  

    Speeds Up Wound Healing 

    Vitamin C is essential for collagen production and wound healing. Acne scars develop as a result of inflammation. The commonest type of scar is known as post-inflammatory hyperpigmentation and fades with time. Using a vitamin C serum can reduce melanin production and this also has a brightening effect on skin. 

    Reduces Scarring

    Deeper acne scars known as ice pick or box car type of scars are due to dermal scarring, for eg due to an acne cyst or an infected acne papule. Since vitamin C stimulates collagen production, it can encourage proper wound healing and reduce the risk of developing acne scars

    Skincare Bible
    In the Skincare Bible, Dr.TWL takes you through a complete study of cosmeceutical actives like vitamin c, hyaluronic acid in an easy-to-read FAQ style.

    Ingredient Pairing Notes

    Vitamin C paired with EGCG results in a complementary effect via the following mechanisms. 

    Focus on Epigallocatechin Gallate (EGCG) 

    EGCG is a well known polyphenol found in green tea. It is primarily regarded as an anti-oxidant ingredient, but it also enhances skin barrier repair. Specifically, by the following mechanisms: 

    1. Enhancing the expression of natural moisturising factor-related genes filaggrin (FLG), transglutaminase 1, HAS-1 and HAS-2
    2. Antioxidant effect 
    3. Prevents free-radical damage associated cell death by downregulating caspases

    A study by Eunji Kim in 2018  found that EGCG exerted a positive effect on skin moisture levels, wrinkles and hyperpigmentation via the above. 

    Vitamin C Serum Benefits Skin Lightening and Anti-Wrinkle

    Why are antioxidants important in antiaging?

    First understand how and why aging occurs. External causes also known as extrinsic aging refer to environmental factors such as UV, air pollution and particulate matter like PM2.5. Intrinsic aging refers to biological aging which occurs because of cell senescence, essentially, when cells grow older they become sleepier. They lose functions gradually until they stop working altogether which is when cancerous cells develop. Aging also causes skin cells to lose moisture, which is why actives like hyaluronic acid are important. HA increases skin moisture by regulating genes known as hyaluronic acid synthase (HAS). Retinoic acid (vitamin A) also effectively regulate HA in the epidermis

    Pre-order Dr.TWL’s upcoming book Skincare & Cosmetic Ingredients Dictionary—a comprehensive workbook for complete mastery of skincare ingredients.

    What are natural moisturising factors? How are they affected by UV damage? 

    NMF are composed of HA and filaggrin, which directly or indirectly affect the skin moisture barrier. NMF themselves are regulated by factors which are not clearly defined. However we know that components of NMF are affected by UV radiation. This is a possible pathway that For example, hyaluronidase which breaks down HA is highly altered by UV radiation. When EGCG is added, it prevents the breakdown of cells caused by UV-damage. 

    How does pairing vitamin C with EGCG improve overall efficacy?

    One of the key ways vitamin C works is by engulfing free radicals generated by UV-damage. It is an antioxidant, which means it fights the oxidative stress. However, L-ascorbic acid itself is also susceptible to UV-damage and when it undergoes oxidation, it will become ineffective. Pairing vitamin C with EGCG preserves the integrity of L-ascorbic acid or SAP formulations as it stabilises the vitamin C extract itself. 

    Skincare Blueprint Newsletter

    In the next tutorial, you’ll learn about enhancing serum absorption, how to properly apply serums and the correct steps to include in your skincare routine. Learn to maximise the benefits of vitamin C serum in your skincare regimen and make every skincare step count. Do you want more skincare tips like this? Subscribe to Skincare Blueprint to receive detailed tutorials in your inbox weekly. Follow Dr.TWL @drteowanlin on Instagram & TikTok.

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