Salicylic acid, also called beta hydroxy acid(BHA), is often found in most skin care products for oily/acne-prone skin. It decreases sebum production and exfoliates dead skin cells. Unlike AHA or PHA, it's oil-soluble, which enables the ingredient effectively unclog pores. It’s one of most beloved, well-known active ingredient for acne treatment, but not without potential negatives such as irritation,redness,or dryness. And it's synthetic substance. On the other hand, Willow bark extract, which is where BHA is drawn from, gives same benefits with much lesser possibilities of drawbacks. After all, it is EWG Green Grade, pH 4-6.