acne
About 85 percent of teens develop acne, like the boy in Figure below . Acne is a condition in which pimples form on the skin. It is caused by a bacterial infection. It happens when the sebaceous glands secrete too much sebum. The excess oil provides a good place for bacteria to grow. Keeping the skin clean helps prevent acne. Over-the-counter products or prescription drugs may be needed if the problem is serious or doesnt clear up on its own.