The serum contains a high concentration of vitamin C, and it also includes various oil ingredients, so it is not as irritating as one might expect. However, there is a slight sense of it sitting on the surface. It would be a good idea to do a patch test.

The ingredient list shows that retinol is present, but it appears that the amount is small based on its placement towards the end. It would be better if the specific amount of retinol was clearly indicated. Vitamin C is primarily used in the morning as an antioxidant, and it is water-soluble. Retinol, on the other hand, is lipid-soluble and is better used at night. Using them together can cause the ingredients to interfere with each other, so it's preferable to use them separately to maximize the effectiveness of each component. If retinol is present, it would be helpful for the product description to clearly indicate that the amount is low enough to not pose a significant issue for daytime use. This would be beneficial for the consumers.

After applying the EGF whitening serum of the same brand once, I apply the vitamin C serum. The volume of 20 ml may seem small, but considering the discoloration, it is difficult to use a large volume, and the skin irritation is not high compared to the high concentration, so I will apply it once and layer it once more to apply a sufficient amount. After applying the pure vitamin C, which can be irritating, applying a serum or cream containing panthenol or ceramides that are good for skin soothing will make the skin feel comfortable!

The high 20% vitamin C content seems to be effective, as the blemishes have disappeared and my face is glowing!!

Due to the high concentration, it can be a bit stinging when using. For oily or combination skin types, it may be better to use it in the evening rather than the morning skincare routine, as it can cause excessive shine.

After using the ampoule, it's best to wait 5-10 minutes for it to be fully absorbed before moving on to the next step. If you're going out, sunscreen is a must!!