Why Vitamin C is one of this dermatologist's favourite beauty ingredients

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Dr. Shreya Andric is a dermatologist based in Sydney. She is passionate about skin health and her mission is to educate the public on how to care for their skin, and also clear up the vast amount of misinformation out there on this topic.

When not at work, Shreya is kept busy by her two young children and loves to spend time with family, friends and occasionally get to a pilates or boxing class!

While Dr. Andric has independently chosen the products that appear in this article, she does not receive revenue from the links. Some of the links may return revenue to Yahoo Lifestyle Australia.

A headshot of Dr Shreya Andric wearing a burgundy blouse
Dr Shreya Andric is a Sydney-based dermatologist on a mission to educate people on how to look after their skin. Photo: supplied.

Vitamin C is one of my favourite active skincare ingredients as it is one of few that has a plethora of clinical trials showing its benefits. 

It is the most present antioxidant in our skin and has numerous benefits. Unfortunately only a tiny percentage of that consumed orally can make it to the skin, which explains why we need to use it topically to see its amazing effects.

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Vitamin C has four different ways of working:

1. It is a potent antioxidant

Environmental factors, such as UV damage, pollution, and smoking can cause damage to the skin through generation of “oxidative stress”. 

Sunscreens are only partially effective in blocking free radicals produced by UV exposure. These can cause skin ageing, pigmentation, broken capillaries, uneven skin texture, and deep wrinkles. 

Vitamin C neutralises this oxidative stress to minimise this damage and studies have found vitamin C to work synergistically with sunscreen to further offset this. It also minimises the level of redness and inflammation caused by the sun and in combination with vitamin E, it has been shown to provide the skin with significant UVA and UVB protection.

Here's what Vitamin C does and how you should use it. Photo: Getty Images
Here's what Vitamin C does and how you should use it. Photo: Getty Images

2. Antiageing effect

Vitamin C is necessary in making collagen. It also stabilises collagen and slows its rate of breakdown. This minimises the appearance of fine lines and wrinkles.

3. Replenishes vitamin E

Vitamin E is also an antioxidant and its main role is in protecting the cells against oxidative stress and maintaining collagen in the skin.

4. Antipigmentary effect

Tyrosinase is an enzyme that converts tyrosine into melanin, which is responsible for producing pigmentation. Vitamin C interacts with copper at the cellular level, blocking tyrosinase and therefore, preventing pigmentation from forming.

The science behind Vitamin C

Vitamin C in topical preparations can be both active and inactive.

The most biologically active and well-studied form is L-ascorbic acid. L-ascorbic acid is hydrophilic (water-loving) and unstable. 

The outer most layer of the epidermis (the stratum corneum) is hydrophobic, which means that without other ingredients, it has poor penetration through this layer. 

Making the molecule more acidic also helps with penetration. Ferulic acid is commonly found in combination with L-ascorbic acid to stabilise the molecule, reduce the pH, and along with tyrosine and zinc, this helps to provide more than 20 times the amount of ascorbic acid found in normal skin. 

It is prone to oxidation so it needs to be used soon after opening. L-ascorbic acid is most effective between 8 and 20%. 

Concentrations higher than 20% have been found to be irritating, with no real further benefit than lower concentrations. 

Those with sensitive or oily/acne-prone skin should choose a concentration less than 10%.

Good examples of products containing L-ascorbic acid include SkinCeuticals CE Ferulic, SkinCeuticals Phloretin CF (for acne-prone/oily skin), Drunk Elephant C-Firma Day Serum, CeraVe Skin Renewing Vitamin C Serum.

SkinCeuticals CE Ferulic
SkinCeuticals CE Ferulic contains L-ascorbic acid. Photo: SkinCeuticals
Drunk Elephant C-Firma Day Serum
Drunk Elephant C-Firma Day Serum is a potent vitamin C day serum packed with powerful antioxidants. Photo: Sephora
CeraVe Skin Renewing Vitamin C Serum
CeraVe Skin Renewing Vitamin C Serum promises to helps to improve skin tone, texture, and hydration. Photo: Amazon

Inactive forms are activated on application to the skin and are therefore more stable. These forms tend to penetrate the skin better, however, there are fewer clinical trials. Examples include:

  • Sodium ascorbyl phosphate – some studies have found this to be as beneficial as L-ascorbic acid. This is less potent (read: gentler) and a good option for acne-prone skin. Example: Ole Henriksen Truth Serum.

Ole Henriksen's Truth Serum
Ole Henriksen's Truth Serum contains sodium ascorbyl phosphate. Photo: Sephora
  • Magnesium ascorbyl phosphate – this is the most stable of the inactive forms, however it has questionable antioxidant properties and is poorly absorbed. These aren’t necessarily bad things as it is a better choice for sensitive skin (The Ordinary Magnesium Ascorbyl Phosphate 10%)

The Ordinary Magnesium Ascorbyl Phosphate
The Ordinary Magnesium Ascorbyl Phosphate is a better choice for sensitive skin. Photo: Priceline
  • Ascorbyl palmitate – this form is very unstable and it is questionable how much it converts to ascorbic acid on the skin. I would probably avoid this one.

  • Tetrahexyldecyl ascorbate – a stable form of vitamin C that is thought to be analogous to L-ascorbic acid. There is less research on this subtype but all the evidence so far is pointing in the right direction! It is lipophilic, which means that it is well-absorbed and can make it through the epidermis down to the basal layer where all the action happens. It does everything L-ascorbic acid does but being a less acidic preparation it is often less irritating. Examples of this include: Sunday Riley C.E.O 15% Vitamin C Brightening Serum, Arbonne DermResults Illuminating Skin Therapy Concentrate

Sunday Riley C.E.O 15% Vitamin C Brightening Serum
Sunday Riley C.E.O 15% Vitamin C Brightening Serum. Photo: Amazon

So, after all this science and long words - how to use vitamin C?!

In the morning, prior to application of sunscreen. 

It can be used twice per day but can be irritating when used with other active ingredients such as retinols/retinoids. 

Also avoid using with benzoyl peroxide as this can oxidise vitamin C.

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