Did you know that vitamin C was the most Googled skincare ingredient of 2020? And yet there are still many of misconceptions about this skincare active.

I was talking to a nutritionist friend of mine who explained that vitamin C as an ingredient is incredibly unstable and she was shocked by how many brands are allegedly using it successfully in their serums and creams. This implored me to do some digging, an attempt to cut through the marketing noise. But much of the information out there is conflicting, so I asked an expert instead.

Dr Alice Rudd is one of Avène's dermatologists and an expert on skin health. She explains that for vitamin C, formulation is more important than percentages and why we need to watch out for oxidisation - this could lead to breakouts.

Can you explain the role of vitamin C in skincare? What are the benefits?

Vitamin C is a powerful antioxidant which helps protect us against free radicals and sun damage. It can help to brighten the skin. It has been found to assist with collagen production and break down pigment and prevent its formation but being a tyrosinase inhibitor.

When and how should we be using vitamin C?

Vitamin C should be used in the morning to harness its full antioxidant potential and allow it to do its work in fighting free radicals. I see some people using vitamin C at night which is a bit of a waste. It should be combined with a daily sunscreen for maximum benefit. Vitamin C also works synergistically with other antioxidants such as vitamin E- so look for products with both.

Who shouldn’t be using vitamin C?

Those with sensitive skin will often find vitamin C to be irritating. It may make those with rosacea more irritated and increase facial redness. I would usually advise that these people do not use vitamin C as it is an acid at the end of the day, and I do not recommend acids in sensitive skins.

If you want to incorporate vitamin C into your anti-ageing routine, a vitamin C precursor can be a better choice. One to try is Avène's A-Oxitive which uses Ascorbyl Glucoside that transforms to pure vitamin C on contact with the skin, and slowly releases it throughout the day – meaning it’s much gentler and better tolerated by sensitive skin. Another advantage of this gradual release formula is that you have ongoing antioxidant protection all day long.

Is it true that it can become unstable in certain forms?

Vitamin C aka ascorbic acid is very unstable and oxidises when exposed to air and light, pollution and ozone. So even though the benefits are theoretically there, by the time it hits your skin, the activity may have been lost. Additionally, formulations of vitamin C that allow stability may penetrate the skin better but are not as potent nor effective once in the skin. It has been found that in addition to ascorbic acid being difficult to formulate, it is not very effective when used as mono therapy so often better combined with ingredients such as vitamin E.

Is it true that vitamin C products only last for three months?

It’s true they oxidise quickly and that they may last even last less if they are not stored properly or formulated properly.

Other forms of vitamin c (precursors/pro-vitamins) can be more stable and packaging can become important for vitamin c- Avène’s A-Oxitive for example is packaged in an airless bottle which protects the formula from oxidation.

What percentage should we look for?

It’s more about the form than the percentage. You generally get best results with the most active form (ascorbic acid)- around 10-15% is ideal. But some skin cannot tolerate ascorbic acid- most skins won't tolerate straight 15% vitamin C. For those with sensitive skin, Avène A-Oxitive defence serum may present a gentler option - It is equivalent to 15% pure vitamin C*.

What’s the best way to use the ingredient for maximum effects?

I recommend use in the morning to prevent damage from free radicals and I like to ensure the formulation is tolerable to the individual skin type.

Is tingling normal when using vitamin C?

Yes for a few seconds because it's an acid. But I don’t advise continued use if the tingling lasts longer than a few seconds or if the skin is red straight after use. Avene A-Oxitive is quite gentle and is well tolerated by sensitive skin types.

What are some vitamin C don’ts?

Do not store in the sun or exposed to too much air when it will become oxidised. Do not persist with use if the skin is becoming irritated or red. And make sure you don’t use it alone, try to combine with other active skin care ingredients to activate synergistically.

*Serum: In-vitro study