Why Vitamin C is still the most powerful antioxidant in skincare
by Bo van Rijzewijk
Everyone's selling Vitamin C. Not everyone understands it.
Walk into any pharmacy or scroll through any skincare brand's website and you'll find Vitamin C everywhere. Serums, moisturisers, eye creams, toners. The ingredient is ubiquitous — which is exactly why most people have stopped taking it seriously.
That's a mistake.
Vitamin C (L-Ascorbic Acid) remains the single most studied, most evidence-backed antioxidant in skincare. Not because it's trendy. Because it actually works — and the science to prove it has been accumulating for decades.
Here's what you need to know.
What Vitamin C actually does
At a cellular level, Vitamin C does three things that no other skincare ingredient does as effectively:
First, it neutralises free radicals. Every day, your skin is bombarded with oxidative stress — from UV exposure, pollution, blue light, and normal metabolic processes. Free radicals are unstable molecules that damage skin cells, break down collagen, and accelerate ageing. Vitamin C donates electrons to stabilise these molecules before they cause damage. Think of it as a daily shield.
Second, it stimulates collagen synthesis. Vitamin C is an essential cofactor in the production of collagen — the structural protein that keeps skin firm and elastic. Without adequate Vitamin C, your body cannot produce collagen efficiently. With it, you're actively supporting the scaffolding that holds your skin together.
Third, it inhibits melanin production. Melanin is what causes dark spots, post-shave marks, and uneven skin tone. Vitamin C inhibits the enzyme tyrosinase, which is responsible for melanin synthesis. The result over time is a more even, brighter complexion.
Why concentration matters
This is where most brands get it wrong — or deliberately mislead you.
Vitamin C works at a specific concentration threshold. Clinical studies show that 10–20% L-Ascorbic Acid is the effective range for visible results. Below 10%, you'll see minimal benefit. Above 20%, you risk irritation without additional efficacy.
Many brands use Vitamin C derivatives — ascorbyl glucoside, ascorbyl palmitate, sodium ascorbyl phosphate — because they're cheaper, more stable, and easier to formulate. The problem is that derivatives must be converted to L-Ascorbic Acid in the skin, and that conversion is inefficient. You end up with a fraction of the active ingredient actually reaching the target.
KLÄR uses 15% stabilised L-Ascorbic Acid. The active form. At the effective concentration.
Why some brands tell you to avoid it
You may have read that Vitamin C is "too harsh" or "not suitable for sensitive skin." This advice comes predominantly from brands that don't use it — because formulating with stable, effective L-Ascorbic Acid is technically challenging and expensive.
The truth is that a well-formulated Vitamin C serum at the correct pH (between 2.5 and 3.5) is tolerated by the vast majority of skin types, including sensitive skin. If you've had a bad reaction to a Vitamin C product, the issue was almost certainly formulation quality, not the ingredient itself.
The bottom line
Vitamin C is not a trend. It's one of the few skincare ingredients with decades of clinical backing across multiple mechanisms of action. If you're using one active ingredient in your routine, this is the one.
Apply it in the morning on clean skin. Give it 60 seconds. Then moisturise.
That's it.