It's normal to get pimples -- about 85% to 90% of all kids do. Simple acne may be the first noticeable sign of puberty. You may get acne on your face, upper chest, or back. During puberty, your oil glands go into overdrive, causing acne. Stress, having your period, and oil-based makeup can make pimples worse. Don't pick them. Instead, keep your skin clean and get treatment advice from a doctor. The good news? Acne usually improves by the end of puberty.