吡咯烷酮羧酸是存於皮膚角質層的自然保濕成份NMF (Natural Moisturizing factor )當中保濕性最強的。

PCA stands for Pyrrolidone Carboxylic Acid and though it might not sound like it, it is a thing that can be found naturally in our skin. In fact, after amino acids, it is the second biggest NMF component of the skin with 12% being PCA of the NMF composition of normal skin. So similar to other NMFs, it's a skin goodie that helps the skin to hold onto water and stay nicely hydrated.

https://incidecoder.com/ingredients/pca