I’ve been applying DIY 20% ascorbic acid solution on my face for a few weeks, and am seeing some benefits already. Photoaging and spots seem to revert a bit, and there is definitely some lightening (as expected [1]). According to some Reddit posts, it takes a few months until the improved collagen synthesis becomes noticeable.
Vitamin C serums are quite expensive because ascorbic acid oxidizes quickly, and other forms have to be used instead. But if you mix ascorbic acid with distilled water yourself, every few days, you get a very cheap and probably more potent alternative. I put it in a sprayer bottle, keep it in the fridge, and spray my face in the morning. I haven’t found studies on the ideal concentration so far, but consensus on Reddit is that anything between 10 and 20% is ideal for collagen synthesis. 20% is too harsh for some.
what's more efficient is taking care of the skin from the inside (so with food - vegetable, outdoor activity, no sun cream needed, always good to protect the head though)
I think the presumption here is that they are white and reducing the look of dark spots and not someone with darker skin lightening it overall.
A challenge with skin-related literature (and internet comments) is that there's always the unspoken assumption that you're talking about a white person unless stated otherwise. Even the article reads oddly of you start off thinking of them as a dark skinned person.
Aging skin usually accumulates pigmentation abnormalities, like hyper- and hypopigmentation. Ascorbic acid might be able to help both. That’s not exclusive to Caucasian skin types btw.
In my case, I‘m just taking it as a sign that it’s working, as pigmentation is only one of the areas AA affects.
Vitamin C serums are quite expensive because ascorbic acid oxidizes quickly, and other forms have to be used instead. But if you mix ascorbic acid with distilled water yourself, every few days, you get a very cheap and probably more potent alternative. I put it in a sprayer bottle, keep it in the fridge, and spray my face in the morning. I haven’t found studies on the ideal concentration so far, but consensus on Reddit is that anything between 10 and 20% is ideal for collagen synthesis. 20% is too harsh for some.
1: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7802860/