Acne can be caused by many different reasons. There are two different overall categories of acne, which are inflammatory and noninflammatory. Within this category, there are blackheads and whiteheads. Salicylic acid is a very well-marketed and beneficial product for this kind of acne. The pore gets hard and clogged and is tender to the touch, resulting in pink inflamed skin around the pore. Nodules are rooted deep within the skin, unlike papules and pustules that rest on top of the skin. They cannot be treated as easily, and require the assistance of a dermatologist.