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Vitamin C, also known as L-ascorbic acid, is an awesome ingredient for skincare. It is one of those ingredients that actually has data to back up the claims. Vitamin C is a powerful antioxidant, protecting the skin from damage done by UV-light or pollution. It also affects collagen synthesis, and as we know, collagen together with elastin are what keep our skin plump. If that is not enough, it has skin lightening effects, helping to fight melasma. It has even been said to have anti-inflammatory properties.
I study chemistry of cosmetics and that includes taking a deep dive into ingredients and how they really work on the skin. Recently I did research on vitamin C and it opened my eyes to the complexity of active ingredients. A great ingredient is not enough: your skin needs to also be able to use it. That is the deal with vitamin C here, and why most serums and creams use vitamin C derivatives.
Vitamin C in skincare: quick answer
Vitamin C can support brighter-looking skin, help with uneven tone and support collagen formation, but it does not replace daily face sunscreen. Pure L-ascorbic acid has the strongest research behind it, but it is unstable and can irritate. Vitamin C derivatives are usually easier to formulate, more stable and often gentler, but they need to convert into active vitamin C on the skin to give the same type of benefits.
L-ascorbic acid, also known as vitamin C in skincare
Vitamin C is an essential nutrient and it occurs naturally in the skin. However, being exposed to UV-light diminishes the amount of vitamin C in the skin drastically. Using vitamin C in skincare can have many benefits.
Vitamin C benefits in a nutshell
Powerful antioxidant
- protects skin from damage caused by UV light or pollution
- helps your skin protect itself from UV damage and repair some damage, but it is not SPF
Affects collagen synthesis
- actually the only ingredient proven to do this. Interestingly many collagen supplements are sold with this claim, but the claim is about vitamin C, not collagen
- collagen together with elastin make your skin plump and youthful; as your skin forms less of these, wrinkles start to form
Anti-inflammatory and depigmenting properties
- there are some studies showing anti-inflammatory properties of vitamin C in treating acne
- it also helps to fight hyperpigmentation and melasma. There are studies of vitamin C derivatives also being able to lighten the skin
All in all, it is an ingredient that works with pretty much all skin types. If you are not sure how active your product should be, start by checking your skin type and your current skin barrier situation.
Vitamin C derivatives: what works best?
Vitamin C is awesome, but pure L-ascorbic acid is a tough ingredient to work with. It is unstable and, because it is hydrophilic and works best in acidic solutions, it penetrates the skin poorly. That is why most beauty products use vitamin C derivatives. These derivatives are stable and can come with different solutions to absorb to your skin better.
You can spot many vitamin C derivatives on the ingredients list by “ascorbyl” or “ascorbate”.
Obviously most of the high claims and benefits are for pure L-ascorbic acid. In order for you to get those benefits, the ingredient needs to transform into L-ascorbic acid on your skin. Luckily there are promising studies on some derivatives doing so, such as Magnesium Ascorbyl Phosphate, Sodium Ascorbyl Phosphate, Ascorbyl Palmitate and Ascorbyl Glucoside.
| Ingredient | Type | Best for |
|---|---|---|
| L-ascorbic acid | Pure vitamin C | Strongest evidence, but more unstable and potentially irritating |
| Ascorbyl Glucoside | Water-soluble derivative | A lighter serum texture and a gentler start with vitamin C |
| Ascorbyl Tetraisopalmitate | Oil-soluble derivative | A more comfortable, skin-friendly feel for drier skin |
| Magnesium/Sodium Ascorbyl Phosphate | Water-soluble derivatives | Stable formulas and sensitive-skin friendly routines |
How to choose the best vitamin C product
If you want to use pure L-ascorbic acid, make sure the concentration is high enough, usually 10-20%. Pay attention to the packaging: is it made so that the ingredients, vitamin C most importantly, are preserved? Preferably not a pipette, but something that closes tightly. The product should also have a lower pH, about 3.5. I am not sure if that happens with most products and, if it does, it can cause irritation.
As to the vitamin C derivatives, those should also be 10-20%. I accept a higher percent too, since it is a derivative. I like the fat-soluble ones. Those are more likely to be accepted by our skin, so I trust their penetration better. Both oil- and water-soluble derivatives are stable, so packaging can be a pipette too, like in the photos.
The best product for you can only be found by trying. If you are building a routine around vitamin C, I would place the serum step after cleansing and before moisturizer; this skincare routine guide explains the order in more detail. And because vitamin C is often talked about with collagen, you might also like my experience with collagen-supporting treatments like microneedling.
Finally I want to note that it is different testing something at the lab than using a lotion at home. It is difficult to say for sure if a product is going to work or not. As to the absorption of vitamin C and its benefits, I guess it is about trying it out and hoping for the best. My logic is that since I am anyway taking good care of my skin, why not use vitamin C if there is even a small chance of improving my skin even further?
Product recommendations
*The Ordinary Ascorbyl Tetraisopalmitate Solution 20% in Vitamin F (Sephora)
Contains an oil-soluble vitamin C derivative.
This lightweight serum also has squalane in it, which is an awesome ingredient in skincare. It is similar to squalene, found in sebum, which is a part of the protective layer of the skin.
*The Ordinary Ascorbyl Glucoside Solution 12% Serum (Sephora)
Water-soluble vitamin C derivative serum.
*The Ordinary Vitamin C Suspension 23% + HA Spheres 2% (Sephora)
Pure vitamin C in a silicone-based serum.
7th Heaven Vitamin C Capsule Concentrates
A good example of air-tight packaging that protects the active ingredient from oxidizing. Contains 22% of vitamin C.
I will update this list as I try new ones. You can also find my current skincare favorites and routine notes on Instagram @charlottaeve.