What is acne? Acne is a term attributed to plugged pores, commonly known as blackheads and whiteheads, pimples, and even cysts or nodules, occur on the face, neck, chest, back, shoulders and upper arms. Follicles, often called pores, often get blocked with sebum (oil), which normally drains to the surface, and a bacteria propionibacterium acnes, begins to grow. Both whiteheads and blackheads start out as a "microcomedone" which then become skin blemishes called comedones. Acne can be upsetting, .