Sankalpita's Post

We all know Vitamin C is highly unstable and reacts easily with oxygen, light, and heat. But these two oxidized much faster than I expected, which was honestly so disappointing. COSRX The Vitamin C 23 Serum – I actually received mine already dark yellow (I even shared a video about it). Even though the brand uses a dark bottle, it doesn’t protect the formula from warm temperatures. COSRX usually keeps their formulas minimal which makes them effective, but not well stabilized. You have to finish this one within a few weeks of opening. It's the fastest-oxidizing Vitamin C I have ever come across. Klairs Freshly Juiced Vitamin Drop (the famous one) – I really like this one because it genuinely brightens the skin, but again, it oxidizes pretty fast, mostly because of its transparent packaging. You have to finish it within 2–3 months of opening, otherwise it might not work the same. Note: Even if you store both products carefully in dark places or even refrigerated, they still tend to oxidize quite easily, especially the COSRX one, sometimes within just weeks. Also, oxidation doesn’t automatically make a serum dangerous, but it definitely makes it less effective. So if it’s turned dark yellow, orange, or brown, it’s most likely oxidized and no longer doing much for your skin.

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This post was published on 03rd November, 2025 by Sankalpita on her Instagram handle "@_sankalpita (Sankalpita Nath)". Sankalpita has total 50.3K followers on Instagram and has a total of 1.2K post.This post has received 210 Likes which are lower than the average likes that Sankalpita gets. Sankalpita receives an average engagement rate of 1.97% per post on Instagram. This post has received 31 comments which are lower than the average comments that Sankalpita gets. Overall the engagement rate for this post was lower than the average for the profile.