Out with the old… old vitamin C serums are not always stable.
For years, companies have raved about how vitamin C serums can brighten and tone skin. But there is one problem - if the vitamin C isn’t stable, it won’t actually work on your skin. Unstabilized vitamin C has already reacted with particles in the air. It is wasted before your skin can make use of it. Think of an apple - when it’s flesh is left in open air it oxidises and turns brown. The same thing happens to vitamin C if it’s not made stable.