You have no items in your shopping cart.
Vitamin C in Skincare: What It Does, and Whether It Can Irritate Skin
Dr Garry Cussell
Skin specialist · Founder, Rejuvaus
The short answer
Vitamin C is one of the most useful antioxidants for skin, but it only delivers when it stays stable and does not irritate. Pure L-ascorbic acid works, yet it oxidises quickly and needs a low, often stinging pH. A true allergy to vitamin C is rare; most reactions trace to that low pH, to oxidised product, or to other ingredients like fragrance. A stable, skin-pH source such as Kakadu plum extract gives the benefits without the sting, which is the approach Rejuvaus takes.
Vitamin C, once tucked away in day creams and brightening serums, has taken centre stage in skincare, and with good reason. Dr Garry Cussell, skin specialist and founder of Rejuvaus, counts it among the three most important antioxidants for the skin, alongside vitamin A and vitamin B3.
The catch is that vitamin C only delivers its benefits when it is stable in the formula and absorbed properly, and when it does not irritate the skin along the way. Here is how it works, whether it can cause a reaction, and how to use it well.
What does vitamin C do in skincare?
Vitamin C is a multi-purpose molecule. It works three ways at once: as an antioxidant, as support for collagen, and as a tone-eveniser.
As an antioxidant, it reduces free-radical damage in the skin, one of the drivers of visible ageing. It also supports collagen: vitamin C interacts with the amino acids that build collagen fibres, and stronger collagen means less creasing and sagging over time. As a tone-eveniser, it helps regulate the pigment-producing enzymes behind uneven tone and sun-related marks, and it supports hydration by aiding the skin's own hyaluronic acid production. Its most useful trait is that it can penetrate well, though how well depends entirely on the form and the formulation.
Pigmentation & Sun Damage
As a natural skin brightener, Vitamin C helps to inhibit pigment-producing enzymes, so you get a more even skin tone. This is a bonus for those of you who are prone to pigmentation caused by sun damage. People who use Vitamin C regularly also tend to get a brighter, more glowing complexion as their natural pigments are more well-regulated.
It also helps with hydration as it aids production of Hyaluronic Acid in the skin.
The most remarkable trait of Vitamin C is that it is one of the few active ingredients that can penetrate deeply, but this also depends on the type of Vitamin C and how it is formulated.
The forms of vitamin C
In skincare you will find pure vitamin C, known as L-ascorbic acid, and a range of derivatives that convert to vitamin C once absorbed. Pure L-ascorbic acid is effective but unstable. Light and air oxidise it, and oxidised vitamin C shifts from a damage-fighting antioxidant into a damage-causing free radical. If a vitamin C serum turns cloudy, dark, or develops an odour, it has oxidised, so stop using it. To stay stable, L-ascorbic acid also needs a low pH, which is a common cause of stinging. Derivatives tend to be more stable and gentler.
| Form | Stability | Irritation risk | In Rejuvaus? |
|---|---|---|---|
| L-ascorbic acid (pure) | Low, oxidises on air and light | Higher, needs pH 2.5 to 3 | No |
| Sodium ascorbyl phosphate | Stable at pH 7 | Low, but less effective | No |
| Magnesium ascorbyl phosphate | Stable at pH 7, water soluble | Low, well-evidenced | No |
| Ascorbyl glucoside | Stable at pH 7, water soluble | Low, releases vitamin C gradually as skin enzymes break it down | No |
| Vitamin C superfruit extract (Kakadu plum) | Stable across pH, does not oxidise on contact | Low, skin-compatible pH | Yes, in Repair & Refine ABC Serum |
How Rejuvaus formulates vitamin C
Most vitamin C serums use L-ascorbic acid. It is effective but unstable, it needs a low-pH formula to stay active, and it oxidises quickly on contact with air and light. The oxidised form, dehydroascorbic acid, is what most often causes the stinging, redness and irritation people blame on vitamin C.
Rejuvaus uses vitamin C superfruit extract from Kakadu plum, one of the richest natural sources of vitamin C on earth. Unlike L-ascorbic acid it is stable at a skin-compatible pH, it does not need an acidic formula, it does not oxidise on contact, and it works alongside niacinamide and vitamin A in the same formula without conflict. If vitamin C has irritated your skin before, the source and formulation pH matter more than the dose.
How to use vitamin C
Vitamin C was traditionally a daytime ingredient and vitamin A a night one, largely so brands could keep the two apart and reduce the chance of irritation. In practice they work well together. Vitamin A supports collagen production and vitamin C helps the collagen synthesise, so as a pair they do more than either alone.
If you are new to both, introduce them slowly, every other day at first, and let your skin adjust. A serum is the best format, more concentrated, with fewer other ingredients competing for absorption. In the Rejuvaus system, vitamin A, B3 and C sit together in the Repair & Refine ABC Serum, blended once, morning and night.
Common questions about vitamin C reactions.
Reviewed by Dr Garry Cussell, skin specialist.
Dr Garry Cussell
is the founder of Rejuvaus and Rejuvenation Clinics of Australia, and a member of the Australasian Society of Cosmetic Medicine. He has practised non-surgical cosmetic medicine for more than 45 years, with a focus on long-term skin health and skincare formulation.
More about Dr Cussell →
