People have been waxing lyrical about the benefits of vitamin C in skincare for a while now, from brightening the skin's complexion and lightening sun spots and pigmentation, to evening skin tone and texture, preventing the appearance of premature ageing, even helping protect the skin from UV damage and pollution.
What many don't realise however, is vitamin C can be a very unstable ingredient - in fact, the higher the concentration, the more unstable and the greater the risk of oxidation.
As Saint Louve founder Elly Seymour explains, oxidation is a chemical reaction that occurs when a molecule is exposed to oxygen and therefore changes, causing active ingredients in the skincare to begin deteriorating. This usually occurs when it's exposed to oxygen, sunlight or warm temperatures.
"The first sign of your serum/cream oxidising is the change in colour," says Elly, who formulated a Lustrum Serum with five potent forms of vitamin C, resulting in 15 per cent better stability.
"You will notice your product turn a dark yellow/orange/brown colour, often followed by a pungent smell.
"The good news is that it probably won't harm your skin, the bad news is that it probably wont do anything for your skin. When the active ingredient, vitamin C, oxidises, it loses its potency and benefit."
The type of packaging you choose helps avoid this happening, and Elly says there are three simple rules:
1. Airless packaging is non-negotiable. This allows no oxygen to get into the ingredients and greatly reduces the risk of your serum oxidising.
2. Opaque packaging. This allows no sunlight to get into the ingredients and reduce their effectiveness.
3. Keep your products below 25 degrees. You can even keep them in the fridge if you like.
Bathrooms can often be warmer than 25 degrees, so it's important to store your products correctly.
