Salicylic acid is a beta hydroxy acid. It is an oil-soluble ingredient so it can penetrate into the pores of the skin. Salicylic acid is also an exfoliant.
Salicylic acid can penetrate deep into the skin to do its job. This precisely makes salicylic acid a potent ingredient to target acne. Salicylic acid dissolves dead skin cells that clogs pores, acts as an anti-inflammatory. It helps acne and pustules go away faster.