Acne is a common skin condition that affects many people of all ages. It occurs when the pores of the skin become clogged with oil, dirt, and bacteria. The clogged pores can become inflamed, resulting in red, swollen bumps called pimples. Acne can range from mild to severe, and can occur on the face, neck, chest, back, and shoulders. The most common type of acne is called acne vulgaris, which is caused by overactive oil glands. It typically appears as whiteheads, blackheads, and pimples on the face, chest, back, and shoulders. Acne can occur in both teenagers and adults and is more common in people with oily skin.