Formulating Serum with Encapsulated Salicylic Acid: Glycols and Gelling Agent

Dipropylene glycol and Pentylene glycol are different chemical substances. Although both are glycols used in cosmetics as solvents, viscosity modifiers, or penetration enhancers, they have different chemical structures and properties.

Regarding the Paula's Choice formula you posted, the team suspects that the high amounts of Dipropylene glycol and Pentylene glycol are used to help dissolve regular Salicylic Acid (BHA), which is poorly soluble in water, and to prevent precipitation.

However, since you are choosing to use Encapsulated Salicylic Acid, which is a special form of BHA that is encapsulated, you do not need large amounts of solvent to help dissolve the Salicylic Acid anymore.

Therefore, the formula recommended by the team, which reduces the amounts of Dipropylene glycol and Pentylene glycol and adds a gelling agent, is more suitable for use with Encapsulated Salicylic Acid.