The application of salicylic acid should usually occur before applying moisturizer. Salicylic acid is a beneficial ingredient commonly found in skincare products designed to treat acne, as it helps to exfoliate the skin and unclog pores. Its main function is to penetrate the skin and remove dead skin cells and excess oil, which can contribute to breakouts. By applying a thin layer of salicylic acid before moisturizing, you allow the active ingredient to deeply penetrate the skin while ensuring that it remains in direct contact with the problematic areas.