This is the best vitamin c serum I have ever used. Gentle on skin no irritation. I can see the difference after using this product. Highly recommended to everyone who is searching for a good vitamin c serum.love love this product.❤️❤️❤️❤️❤️❤️

I've purchased this many times. It's just a good vitamin c product. It is sealed tight in a very opaque glass bottle. It is fresh until you open it. I may be accustomed to using ascorbic acid so I found the formula to be gentle. Still be advised that I did occasionally experience a little warmth to my face when first applying it. It is a high percentage of pure ascorbic acid. Cosrx goes on sale all the time so you'll find a good deal on it year round.

cosrx , you can't go wrong with the serum product . I use this after toner , twice a week , I have some acne spots , this brighten my skin

I saw some improvement, keep it in the fridge always

My skin brightened after a few use. If you're planning to use it in the morning, make sure to use sun screen after.