quote:

There is confusion here because of chemical names.

PCA usually means Pyrroline carboxylic acid. This molecule attract water and is used in many skin products to wet the outer skin proteins.

But GHK also has a name (the FDA requires non-chemical names also) which is Prezatide Copper Acetate which has also been called PCA. So this produces some confusion.

Glycerin also attracts water to the skin's surface and is used at a high concentrations in moisturizers. But our use of glycerin is about 1 to 2%, where it functions as a slipping agent and does not attract any significant water.