Introduction Acne is unique among all medical conditions. Are there any other medi- cal conditions that affect almost every single person in the world at some point in their life? Are there any other medical conditions that are so visible and that so commonly affect people who are at the most sensitive period of their lives? I hope that this book adequately addresses the most special and fas- cinating condition that we refer to as acne. It is a condition that is so common, and yet it can be so hard to find a comprehensive and accurate source of knowledge on the topic. The Internet can be a clash of conflict- ing sources, and adolescents, teenagers, and young adults can have a hard time knowing where to turn. Therefore, I hope that this book can serve as a source of accurate and insightful knowledge regarding acne. From the basics of what acne is, what causes acne, and how acne is treated, this book hopes to tackle the most common questions that der- matologists and other physicians are asked regarding acne. During a der- matology appointment, there are typically only a few minutes available to diagnose acne, prescribe a treatment, and educate a patient regarding his or her acne. This book is a collection of all the knowledge that I wish I could share with each of my acne patients. In fact, I wish that every person in the world could know all of the information that is in this book. Acne is so common that it is almost less like a medical condition and more like a commonly shared human experience.