I bought a vitamin C ampoule because my face was yellow, but it stung so bad I almost threw it away ㅠㅠ (Honest review)

Lately, when I look in the mirror, my complexion is kind of sallow ;; I thought it was because I didn't get enough sleep, but it was just because I got old and dull ㅡㅡ So I bought a famous pure vitamin C ampoule to quickly whiten my skin? Wow, but as soon as I applied it, my face burned and stung, I thought all my skin was peeling off ㅋㅋ

I looked it up and found out it's because it's naturally acidic, so I was about to give up, but I felt bad about it, so I mixed a drop into my moisturizer and applied it. It seemed to be more tolerable. I've been applying it only at night for about two weeks now, and when I wash my face in the morning, my skin tone definitely feels brighter. My freckles haven't completely disappeared, but my overall skin tone feels brighter, haha.

But this is really tricky to store ;; I keep it in the fridge and use it, but I'm worried that the color will change already.. And they say sunscreen is essential if you apply it during the day, but I'm scared, so I just apply it at night ㅋㅋ The most certain way would be to go to Maypure and get a toning treatment, but I'm going to try everything I can at home for now. How do you guys take care of your whitening skin? Are oral vitamins effective? Please give me some recommendations ㅠㅠ