The Ingredient Series: Vitamin C

July 08, 2021
1.1 k visits


As brands become more transparent with their ingredient lists, skincare seems to be getting more and more complicated. The Ingredient Series aims to look at popular ingredients in the skincare industry and demystify their roles and whether you need them in your routine or not.

For our first instalment, we are going to cover Vitamin C – a very popular ingredient and for good reason!


What it does and how


Vitamin C has decades of veritable clinical testing backing its three golden claims – antioxidant, anti-ageing and skin brightener.


Antioxidant: Terms like free radicals and antioxidants are thrown around a lot but what do they mean?

In short, a free radical is an atom missing an electron. They can be a normal by-product of your cell metabolism but they are also created by other environmental factors, like UV rays, cigarette smoke, stress etc. Due to missing an electron, free radicals are very reactive and damage cells in their vicinity in an attempt to obtain this missing electron. In the skin, this damage is to skin cells and can lead to early signs of ageing, pigmentation and sometimes cancer. Free radicals cannot be eliminated, but one way of minimising their damage is to use an antioxidant product.

An antioxidant is a molecule that can neutralise a free radical. The antioxidant and the free radical combine, and thus prevent the damage caused by the free radical in the skin. Vitamin C has been extensively studied and is a very effective antioxidant!

By minimising this skin damage, Vitamin C is an effective preventative anti-ageing product.


Anti-ageing: In addition to preventing signs of ageing, Vitamin C also directly acts against it by promoting collagen synthesis. Collagen is responsible for the integrity of your skin and loss of collagen is a big cause of wrinkles and sagging. Very few ingredients are proven to boost collagen so Vitamin C is quite unique in being able to do this!


Brightening: Last but not least, Vitamin C is highly effective in treating melasma and hyperpigmentation. Vitamin C inhibits melanin production in the skin, which leads to lightening hyperpigmentation (which can appear from sun damage or from inflammation in the skin e.g. post-acne scars) and evening out skin tone. 

In short, Vitamin C prevents ageing by being a great antioxidant, directly minimises signs of ageing by boosting collagen and minimises hyperpigmentation by inhibiting melanin production.



Types of vitamin C

When we say Vitamin C, we are usually talking about a family of molecules. The gold standard molecule – pure vitamin C – is called L-Ascorbic Acid. When we talk about Vitamin C being an amazing ingredient that can work as an antioxidant, anti-ageing and brightening product all in one, it is L-Ascorbic Acid. Almost all studies carried out in vivo (which means human participants) look at this molecule. However, its big drawback is that it is very unstable and thus, difficult to formulate.


Due to being so unstable, many other Vitamin C derivatives have been formulated. Vitamin C derivatives need to 1) be able to penetrate the skin and 2) be converted into an appropriate amount of L-Ascorbic Acid in the skin. This is because L-Ascorbic Acid is the active form that has the great results we’re after. The biggest drawback of any derivative is that there are few relevant in vivo studies – most studies are in vitro, meaning in a petri dish! As promising as any derivative appears to be in vitro, it is difficult to know if it will do the same thing in real human skin – so take all claims with a pinch of salt.



A note on percentage:

Some skincare brands have started labelling their ingredient percentages, which is a great move towards transparency in formulations. However, this can lead to the misconception that a higher percentage is better, which is not necessarily true. L-Ascorbic Acid must be at least 5% in order to have any effect, but studies show that over 20% it doesn’t have any added benefits and can cause significant skin irritation. If you are looking for an Ascorbic Acid-based serum, we recommend 5% if beginner/sensitive and 10-15% otherwise. Note that derivatives work at different percentages, so this rule does not apply to them.




L-Ascorbic Acid (AA)

Gold standard vitamin C

Many many studies back up its efficacy in-vivo

Very unstable, oxidises easily

Ascorbyl glucoside

Very promising in vitro studies

3-O Ethyl Ascorbic Acid

Promising in vitro studies, strong point appears to be brightening

Magnesium ascorbyl phosphate (MAP)

No data on antioxidant properties, but in vitro studies suggest it can boost collagen and brighten

Sodium ascorbyl phosphate (SAP)

In-vivo studies confirm antioxidant properties, though less so than AA

In-vivo trade publication also suggests it may be a good brightener

In-vitro studies show it can boost collagen, but less effectively compared to MAP

In-vivo studies show anti-acne properties

Tetrahexyldecyl Ascorbate (TDHA)

Only in vitro studies

Ascorbyl Tetraisopalmitate (ATIP)

Only in vitro studies

Ascorbyl Palmitate

Least studied molecule and least promising – falls short in almost all areas and appears to be almost as unstable as AA too!


If a derivative doesn’t have in vivo studies, this doesn’t mean it’s ineffective – it means we don’t yet have data to prove it is or isn’t effective. More studies are being done and eventually, we will have proof either way for these derivatives. In the meantime, if you are seeing benefits from a certain serum, keep using it!




We’ve spoken a lot about how pure Vitamin C is unstable – but what does that mean exactly?


Well, Vitamin C is unstable because it can easily oxidise – leave it in the sun and it quickly turns brown. Oxidising is equivalent to going off. Once Vitamin C has gone off, it provides little of the benefits we’ve spoken about.


The original colour of a Vitamin C serum should be clear. Clear Vitamin C is not oxidised and works. This colour will in time turn from clear to a dark orange-brown. If it’s gained a bit of colour, it should still be viable. Once it’s turned the dark colour that can be seen in the photo, it is no longer viable and should be thrown out. Putting it on your skin at this stage will have almost none of the Vitamin C benefits. 


Credit to skinscience.md


Should you use a vitamin C?


Yes! Due to its many roles, vitamin C is great at all ages, from teens to old age. If you want to prevent ageing, it’s a great antioxidant. If you are struggling with pigmentation, it’s a great skin brightener. If you have mature skin and want to target signs of ageing, it boosts collagen. There’s a lot to love about Vitamin C!

For a beginner, we recommend starting with 5% L-Ascorbic Acid or adding the serum to your moisturiser to minimise initial irritation. If you find you do not tolerate L-Ascorbic Acid, try one of the derivatives.

The many different formulations and derivatives can be confusing but we’re hoping this article sheds a bit of light on this superstar ingredient. 


An AI platform for healthier skin and a happier mind

Learn how to manage your condition better, receive the emotional support you need, and stay on track with your skincare routine!

Try for free


5 Common Misconceptions About Acne
Previous post

Recommended for you

The impact of skin condition on your mental health

Sleep hygiene is all about building good sleep habits and attitudes

Explanations about the most common acne misconceptions

An AI platform for healthier skin and a happier mind

Learn how to manage your condition better, receive the emotional support you need, and stay on track with your skincare routine!

Try for free
Learn more

Leveraging technology, Skinlync provides user journey support and services that cover 3 key support principles: psychological support, access to reliable and safe resources and data collection and analysis.

Learn more
Make Skinlync yours

Learn how to manage your condition and symptoms, receive emotional support from experts and others like you, and track your condition and skincare routine. We want to help you attain healthier skin and a happier mind.

Share your story

If you have a story to tell, knowledge to share, or a perspective to offer - welcome home. It’s easy and free to join Skinlync and post your thinking on anything about skin and wellbeing.

Write on Skinlync
Copyright © 2022 Skinlync - All Rights Reserved. Information on Skinlync is reported by our members and is not medical advice.

We use cookies to ensure that you get the best experience. Want to know more? Read our Cookie Policy.