" Acne A skin condition that causes spots and pimples is Acne. It usually appears on the face, forehead, chest, upper back, and shoulders. It is one of the most common skin conditions in the United States, affecting 50 million Americans yearly. Causes Acne occurs for all ages, but is most common for teens and young adults. In fact, 85 percent of people who have acne, are between the ages of 12 and 24 years. Some ...