Acne is a common condition affecting about 17 million Americans. Acne occurs most often among teenagers — nearly 4 out of every 5 teens have acne. The condition usually first appears between the ages of 10 and 13. In most cases, acne lasts for about 5 to 10 years, then goes away on its own. However, some adults in their 20s, 30s, and even 40s get acne.