How To Choose The Best Vitamin C Serum: Everything You Need To Know

korean skincare anti-aging fading dark spots fading hyperpigmentation vitamin c serums best vitamin c serums

Unlike in Western skincare culture, skin brightening is probably the highest ranking skincare concern in Korean and Japanese skincare. No matter what type of hyperpigmentation your skin has (such as acne scarring, sun damage or melasma) – a vitamin C serum is a must have in your skincare routine if you’d like to brighten your skin.

But how does a vitamin C serum work and what should you look for in a vitamin C serum? Where does a vitamin C serum fit into your skincare routine? And can you use it with other skincare products such as BHA, AHA or niacinamide?

I’ll be answering all these questions in this post!

What Is Vitamin C And What Are The Skincare Benefits of Vitamin C?

We all know how important vitamin C is nutritionally in our every day diet, but did you know that it’s also a powerful ingredient with many benefits when it comes to skincare too?

Vitamin C is simply a water-soluble nutrient that acts as an antioxidant in the body by protecting cells by the damage caused by free radicals (known as oxidative damage). This of course, includes skin cells – vitamin C can help to fight free radicals and prevent damage caused by ultraviolet light (AKA sun damage).

Not only is vitamin C good at fading hyperpigmentation and general skin brightening – it also can help to reduce fine lines and wrinkles (by boosting the skin’s collagen production and decreasing trans-epidermal water loss) – making it the perfect anti-aging ingredient!

Who doesn’t want brighter, firmer and plumper skin?

How Does Vitamin C Fade Hyperpigmentation?

Without going too much into the biochemistry – what makes vitamin C such a sought after ingredient when it comes to fading hyperpigmentation?

Vitamin C reduces the activity of tyrosinase (an enzyme involved in the formation of melanin in skin cells) by interacting with copper ions at the tyrosinase active site. Or, in other words- it inhibits the production of melanin – thereby preventing hyperpigmentation.

hyperpigmentation sun damage dark spots how it occurs melanin production vitamin c serums korean skincare
Without going into too much of the biochemical pathway – you can see in this pretty diagram how sun damage (or skin darkening) occurs in the presence of UV light. Always wear a high SPF/PA sunscreen!

I want to point out something very important here. The keyword above is prevention. Vitamin C actually only prevents hyperpigmentation – it cannot fade hyperpigmentation that is already there. It is therefore so important to wear a high SPF/PA sunscreen every day (to prevent new hyperpigmentation from forming) and use ingredients such as alpha-hydroxy acids (AHAs) or beta-hydroxy acid (BHA) to increase the cell turnover rate of your skin (to reveal newer and brighter skin). Without these additional steps (especially in regards to wearing sunscreen), you would likely not see any affects when using a vitamin C serum and would be wasting your valuable money.

Related article:

Can I Use A Vitamin C Serum To Fade Post-Inflammatory Hyperpigmention – AKA Acne Marks

One of the most common skin concerns that people have is acne marks, also known as post-inflammatory hyperpigmentation (PIH). Acne marks differ from acne scars (depressions left in the skin) in that they look like a spot that is a darker color compared to the rest of your skin.

Both acne marks and acne scars form when the skin’s natural healing process is disrupted after a breakout. Acne scars are usually permanent and require dermatologist treatments (such as laser or dermal fillers) to minimize their appearance. Acne marks on the other hand can fade away naturally over time (over about 3 to 6 months as your skin cells turnover).

Vitamin C can be used to speed up this process of fading PIH. This is due to its ability to stimulate the production of collagen, which speeds up the healing process. Vitamin C also helps to fade PIH by inhibiting the production of melanin (which can darken spots, especially in the sun). Just don’t forget your sunscreen during the day!

What To Look For In A Vitamin C Serum

There a few things to consider when choosing a vitamin C serum. This includes: what form of vitamin C the product contains, what percentage of vitamin C the product contains (the concentration), what type of packaging the serum comes in and what other beneficial skincare ingredients the product may be formulated with.

best korean vitamin c serums how to choose vitamin c serum
Some of the things to consider when choosing a vitamin C serum. Read on to find out what is best.

What Form Of Vitamin C Is The Most Effective At Fading Hyperpigmentation?

There are many forms of vitamin C, including:

  • ascorbic acid (also known as L-ascorbic acid or L-AA)
  • sodium ascorbyl phosphate
  • ascorbyl palmitate
  • retinyl ascorbate
  • tetrahexyldecyl ascorbate
  • magnesium ascorbyl phosphate
  • ascorbyl glucoside, and
  • 3-O ethyl ascorbic acid (a relatively new form)

However, some forms work better than others – so it’s important to pay attention to this when buying a vitamin C serum.

For maximum anti-aging and skin-brightening properties, it’s best to choose a product containing L-ascorbic acid as it is the form of vitamin C with the most skin-related research behind it. It has also consistently shown to be the most effective form at penetrating the skin barrier.

L-ascorbic acid is sadly a highly unstable ingredient – meaning that it oxidizes (breaks down) quite easily when exposed to light and air (making it ineffective). It’s therefore important to verify that the L-ascorbic acid in your serum is stabilized (more on that below).

The other two forms of vitamin C which also work well for anti-aging purposes are tetrahexyldecyl ascorbate and magnesium ascorbyl phosphate.

Related article:

The Importance Of Vitamin C Concentration In Serums

The efficacy of a vitamin C serum is proportional to the concentration, meaning that the higher the concentration of vitamin C in a product- the more effective it is at brightening the skin.

Studies have shown that even a vitamin C concentration as low as 0.6% provides antioxidant and anti-aging benefits to the skin – HOWEVER – a concentration of 20% has been shown to have the greatest effect on fading hyperpigmentation. Studies have also shown that concentrations above 20% don’t result in higher efficacy.

Serums containing a large amount of vitamin C usually do state the concentration. If the serum you are using (or would like to purchase) doesn’t state the concentration, then it’s likely that it contains a smaller amount of vitamin C.

Preventing Vitamin C Oxidation: The Importance Of Product Packaging And Storage

All antioxidants degrade very fast when they come in contact with the air (oxygen) or sunlight, and vitamin C is no exception!

I highly recommend only buying a vitamin C serum that comes in a dark glass, opaque (not clear) bottle as this is the most stable way to store them – ensuring that you will get the best possible results from your skincare product. Since the glass bottles tend to come with a dropper and not a pump, this makes contact with oxygen inevitable, so my advice here is to only open one serum at a time. I also give my vitamin C serum a 3 month shelf life once opened, although I have heard people getting away with up to 6 months.

klairs vitamin c serum best korean vitamin c serum clear bottle oxidation
Exception to the rule: this popular Klairs Vitamin C serum is formulated to make it more stable – which is why it’s sold in a clear bottle.

I actually store my vitamin C serum in the fridge to keep the shelf life as long as possible (as heat can also cause your product to degrade).

If you find that your vitamin C serum has changed to a tan or brown color, then it means it has oxidised. Never apply an oxidised product as it will generate free radicals in your skin – thereby causes damage instead of preventing it.

Other Beneficial Ingredients That Work Well With Vitamin C

vitamin c serums vitamin e ferulic acid niacinamide beneficial ingedients korean skincare tips
What ingredients should your vitamin C serum contain? I’ve already talked about L-AA being the preferred form of vitamin C, but there are a few other beneficial ingredients that work well with vitamin C (and yes, niacinamide is one of them).

The effectiveness of vitamin C has been shown to be greatly increased when combined with other powerful antioxidants such as vitamin E and ferulic acid. This is thought to be because when used together, they support each other’s antioxidant function.

For example, vitamin E enhances the antioxidant effects of vitamin C when they are applied to the skin at the same time. Both vitamin C and vitamin E also play a role in protecting your skin cells from sun damage because they neutralize the free radicals generated during UV exposure. So therefore, having both vitamins available in your serum helps prevent sun damage better than either vitamins on their own.

Vitamin C and vitamin E also work together to maintain healthy collagen, a protein important for skin strength. Vitamin C is needed to help synthesize collagen, and vitamin E is needed to maintain proper cross-links between collagen fibers.

Ferulic acid is also a potent antioxidant, naturally occurring in the cell walls of plants. Skincare related studies have shown that it has the ability to enhance the affects of both vitamin C and vitamin E. It is believed that ferulic acid increases the stability of vitamin C in water solution and also almost doubles the effectiveness of both vitamin C and vitamin E’s ability to protect the skin against UV damage.

So, when searching for a vitamin C serum, I highly recommend choosing one that also contains either vitamin E or ferulic acid – or even better – BOTH!

When To Use Vitamin C In Your Skincare Routine?

You can apply your vitamin C serum either in the morning or the evening. Many people prefer to apply it during their morning routine due to its photo-protective effects. Just remember, it only boosts your sunscreen’s protection – it doesn’t replace it!

how to use vitamin c serum korean skincare routine
A pretty picture guide I made to show where vitamin C belongs in your skincare routine.

In terms of when to apply your vitamin C serum in your routine, you would apply it after you use your cleanser(s) and/or cleansing or pH balancing toner, and before you apply any hydrating products (such as a hydrating toner) or products with oils or fats in them (such as a moisturizer or sunscreen).

If you are using other actives in your routine, you would apply the vitamin C serum first, followed by BHA and last, AHA. Unless your skin tolerates actives very well, I would recommend perhaps applying the vitamin C serum in the morning and your BHA and/or AHA in the evening, or even better – using them on alternate days.

As with most actives, vitamin C also requires a 15-20 minute absorption window because it is pH dependent (L-ascorbic acid in particular). This just means that you need to wait 15-20 minutes after applying your vitamin C serum before you proceed to applying the next product in your routine.

Can I Use Vitamin C And Niacinamide Together?

So I’ve already told you about the benefits of vitamin C. Well, niacinamide is another ingredient with loads of skin benefits. On it’s own, niacinamide is a skin-restoring ingredient that can visibly improve the appearance of enlarged pores, fine lines, and dull skin.

So therefore, it’s a very common question is: Can you use both vitamin C and niacinamide in your skincare routine?

There are two myths floating around on the internet that these two ingredients should not be mixed:

  1. Using vitamin C and niacinamide together neutralizes the effectiveness of both ingredients, and
  2. When used together, you might create a substance (nicotinic acid) that leads to skin redness.

But, MYTHS BUSTED! Long story short: some old research from the 1960’s was interpreted incorrectly. You CAN actually use both vitamin C and niacinamide together! Research has shown that it won’t lead to skin problems and combining the two ingredients actually leads to a wealth of skin benefits.

Related article:

Can I Use Vitamin C And Retinol (Vitamin A) Together?

Retinol (a form of vitamin A) is an ingredient that provides many skincare benefits, including promoting skin renewal and enhancing collagen production). It is also a powerhouse ingredient when it comes to fading sun damage (you can read more about retinol in my hyperpigmentation post).

All of the above benefits make it a particularly popular anti-aging ingredient for woman over 30. But can you combine retinol with your vitamin C serum? Again, there is a lot of misinformation floating around the internet, which says that the two ingredients should not be combined (mainly due to their differing pH levels).

However, research has again busted this myth, showing that vitamin C and retinol CAN in fact be used together (we now know that acidity doesn’t deactivate retinol). Researchers found that a combination of antioxidants actually provides optimal results – as they work to boost each other’s effectiveness. Vitamin C was found to help retinol work better by stabilizing it, and in turn extending its effectiveness.

If however, you are still concerned about combining these two ingredients (or if you have very sensitive skin), you could include a waiting time in your routine. In this case, you would apply your vitamin C serum first, and wait 30 minutes until your skin returns back to its normal acidity (pH of approximately 5.5), and then follow up with a retinoid. Another way to play it extra safe would be to use a serum containing a vitamin C derivative instead of ascorbic acid, or using your vitamin C serum in the AM and your retinol in the PM.

The Bottom Line

Vitamin C is a powerful ingredient to include in your skincare routine if you would like to fade hyperpigmentation, whether it’s sun damage or post inflammatory hyperpigmentation following acne breakouts.

There are a lot of vitamin C serums on the market, but my tips are to look for a serum packaged in a dark glass bottle to prevent the product from oxidizing too soon. The higher the concentration of vitamin C in the serum, the better too (20% is the optimal amount).

Also, look for serums that include other beneficial ingredients such as vitamin E and ferulic acid (which optimise the effectiveness of vitamin C). Research has also shown that it’s okay to use niacinamide and retinol together with vitamin C, although there are myths floating around that it’s not wise to do so.

Lastly, don’t waste those valuable drops of your vitamin C serum by forgetting to apply a high SPF/PA sunscreen every day!