Acne is the term for the blocked pores (blackheads and whiteheads), pimples, and deeper lumps (cysts or nodules) that can appear typically on the face, neck, chest, back, shoulders and upper arms. Seventeen million Americans currently have acne, making it the most common skin disease in the country. While it affects mostly teenagers, and almost all teenagers have some form of acne, adults of any age can have it. Acne is not life-threatening, but it can cause physical disfigurement (scarring) and emotional distress.