Salicylic acid peels (aka beta hydroxyacid peels to distinguish them from alpha hydroxyacid peels, like glycolic acid) can play a very useful role, in combination with topical and oral therapies, for treating acne vulgaris. Unlike other superficial peeling agents, including the alpha hydroxyacids, salicylic acid possesses the distinct advantage of being lipid-soluble, meaning that it can penetrate down the oil gland pores where the acne process gets started and progresses.
I have been using salicylic acid peels successfully, in the form of in-office treatments, in maximal concentrations (as opposed to low strength home peels) for many years with gratifying results in concert with topical anti-acne medications, such as retinoids, azelaic acid, and benzoyl peroxide. Typically a series of four treatment sessions, spaced at two to four week intervals is needed to achieve optimal results.
Since post-inlammatory hyperpigmentation (PIH), the blotchy and aesthetically troubling skin staining that follows as the aftermath to active acne lesions, plays such a significant role in the whole acne evolution, salicylic acid, which can help to fade these stains, can additionally play a significant role in reducing the degree of post-clearing dyspigmentation and its duration, which, if left to spontaneously resolve, may last for many weeks to month.
I have found that OTC salicylic acid preparations, which contain very low percentages (typically about 2%) can be helpful, as well, in acne treatment, but cannot compare in speed of response and overall efficacy to the in-office, high potency versions.