Azelaic acid will help treat acne, whiteheads, and blackheads, as well as redness, rosacea, oily skin, and hyperpigmentation. Salicylic acid has strong exfoliating powers, and it is used to treat mild acne, blackheads, and whiteheads. Azelaic is great for lightening and brightening your skin, while salicylic acid helps reduce inflammation and decrease oil secretion. Both are great products and can be used together. You should choose the one that will benefit your skin the best.