What Is Vitamin C? Benefits & How It Works for Skin

What is Vitamin C (Ascorbic Acid)?

Vitamin C is a water-soluble vitamin and one of the most researched antioxidants in skincare. In its purest form it is called L-ascorbic acid. Our bodies cannot make it, so we get it from foods like amla, oranges and guava, but putting it on skin has different effects from eating it.

In skincare, vitamin C is used to brighten dull skin, fade dark spots and support collagen. It is also known for being fragile: it breaks down when exposed to air, light and water, and it needs a fairly acidic formula to work. This is why there are many vitamin C 'derivatives', which are covered on their own pages.

Source

Found in	Ascorbic Acid (INCI name)
Origin	Found in citrus fruits, amla and guava; cosmetic grade is made in a lab
Also known as	L-ascorbic acid, pure vitamin C, vitamin C

Top features and benefits

Powerful antioxidant protection	Helps fade the look of dark spots	Brightens dull, tired-looking skin
Supports collagen production	Helps even out skin tone	Boosts the effect of sunscreen
Helps soften the look of fine lines	Used in serums, usually for morning	Well studied for decades

How Does It Work?

Every day, sunlight and pollution create unstable molecules called free radicals that damage skin cells and speed up ageing. Vitamin C is an antioxidant, which means it steps in and neutralises these before they cause harm. When applied under sunscreen, it adds an extra layer of protection, although it does not replace sunscreen.

Vitamin C also helps skin make collagen, the protein that keeps skin firm and smooth. It also interferes with the enzyme that makes melanin, which is why it can lighten dark spots and give skin a brighter look. These effects build slowly, and most people need a few months of regular use.

For L-ascorbic acid to work, the product needs enough of it, usually between 8 and 20 percent, and a low pH around 3.5 or lower. Studies suggest going above about 20 percent adds no extra benefit and may only irritate. Formulas with vitamin E and ferulic acid have been shown to be more stable and to add extra protection. It can sting, so start slowly and use a product that is stored in a dark, airtight bottle.

Frequently Asked Questions

What does vitamin C do for skin?

It acts as an antioxidant, helps brighten dull skin, fades dark spots and supports collagen, which helps skin look firmer over time.

What strength of vitamin C is best?

For L-ascorbic acid, research supports about 8 to 20 percent. Higher strengths do not add more benefit and are more likely to irritate.

Should I use vitamin C in the morning or at night?

Morning is popular because vitamin C adds antioxidant protection under sunscreen. It can also be used at night if that suits your routine better.

Can vitamin C be used with niacinamide?

Yes. They are commonly used together and are considered compatible for most people. If your skin stings, use them at different times of day.

Can I use vitamin C with retinol?

Yes, many people use vitamin C in the morning and retinol at night. That keeps things simple and reduces the chance of irritation.

Why does my vitamin C turn orange or brown?

It means the vitamin C has oxidised, or broken down, after exposure to air or light. It is usually less effective at that point, so it is best to replace it.

Does vitamin C make skin sensitive to the sun?

No. Vitamin C is an antioxidant and does not cause sun sensitivity. You still need sunscreen every day.

Is vitamin C safe for sensitive skin?

L-ascorbic acid can sting, especially at high strength. Sensitive skin may do better with a lower strength or a gentler derivative. Patch test first.

How long does vitamin C take to work?

Glow can improve in a few weeks, while dark spots and fine lines usually take around 3 months of daily use.

What is the difference between vitamin C and its derivatives?

Derivatives like Ascorbyl Glucoside and Magnesium Ascorbyl Phosphate are more stable and gentler, but need to be converted into vitamin C by the skin. They are generally less proven than L-ascorbic acid.