It's for sure not 100% Centella, according to EU law - there are ingredients below 0,1% or 0,01% (I do not remember it correctly) that doesn't have to be mentioned so I guess this serum has some preservatives, antimicrobial as well as buffer or thickening ingredients. I'm not sure how about other countries and how the law regarding to ingredients is but the same thing is with mugwort essences or even Artemisia mask from Missha - it wasn't 100% Artemisia Mask or essence, especially if we think about sheet or gel mask, it was just impossible :) So don't be scared, but still I would recommend to observe the serum. Not all korean products have so called PAO date on packaging but I would also stick to PAO - a tiny jar with information how many months after opening should you use product before it goes bad :)