Hi Candidate,

Before proceeding with the Reactions, let us know about both these acids- Thio- glycolic is an AHA (alpha hydroxy acid), it works better at the surface of the skin. The salicylic acid ingredient is a BHA (beta hydroxy acid and is stronger in acidic nature as compared to thioglycolic acid.

Since acids require basic medium for Reaction, but in acidic medium the less stronger acid will act as Base and will react with the stronger Acid with its Thiol group from the acidic environment.

Hope that this answer helps you.