percentage of free acid is needed for salicylic acid to be effective against
acne? If a product containing 2 % salicylic acid has a pH of 3, then only 0.97 %
of it will be in its free acid form. That seems to be an extremely low number, especially
when learning that only the uncharged form can be absorbed through the skin. I haven't been able to find any specific answers on google scholar.