Acne is a common skin disease that causes blackheads, oily skin and pimples. Pimples form when hair follicles under your skin clog up with oil. Most pimples form on the face, neck, back, chest and shoulders. Anyone can get acne, but it is common in teenagers and young adults. Severe acne can lead to scarring. Poor diets, including sugar, soda and junk foods cause acne and are associated with insulin-resistance and diabetes. Hormone changes, such as those during the teenage years also play a role. Mild acne can usually be cured with a prescription retinoid cream in just a few weeks; more severe forms can also be successfully treated, so see your dermatologist.