This is what salicylic acid actually does to your skin
Salicylic acid sinks deep down into the skin, where it is able to dissolve pore-clogging skin debris. It is thought that this debris, made from old skin cells, is one of the causes of acne. The dead skin cells should in a healthy skin renewal cycle just slough off, but when they do not do so and instead stick around clogging the pores and creating pimples, salicylic acid gets right down in there and loosens up the junk cells so they can be rinsed down the sink next time you wash your face.
Dr. Naissan O. Wesley explained to Allure that salicylic acid “dissolves skin debris that clogs pores, [acts] as an anti-inflammatory, and also helps red inflamed pimples and pustules go away faster.” But dermatologist Rachel Nazarian does have one caveat: While salicylic acid is very effective against blackheads and whiteheads, it is somewhat less effective against cystic (red) acne.