Years ago, teenagers with acne were told to cut out the potato chips and given a tube of Clearasil. Today, we know far more about the reasons why some people develop acne and how it can most effectively be treated. All cases of acne are not created equal, and neither are all acne treatments. Although all acne has its roots in the same process -- hormonal fluctuations that stimulate oil production -- not all acne is equally severe and not all cases of acne will respond to the same types of treatments. Most cases of acne fit within one of three main categories, says Macrene Alexiades-Armenakas, MD, PhD, an assistant clinical professor of dermatology at Yale School of Medicine and a specialist in laser therapy for acne, who practices in New York City: Comedonal acne. This is the kind of mild acne that involves blackheads and whiteheads. It forms because a component of skin oil called sebum, along with old skin cells, block the pores of the skin. Comedonal acne appears most often on the forehead, nose, and chin. Inflammatory acne. This form of acne occurs when the area just under the “plug” (the blackhead or whitehead) becomes reddened and inflamed. Cystic acne . The most severe form of acne, cystic acne develops as the result of an actual infection in the area of the outbreak. Cystic acne often runs in families. It’s often very painful and can result in disfiguring, permanent scarring. The type of treatment that works for you will depend both on the kind of acne you have, and the additional factors that seem to trigger acne outbreaks. Treating Mild to Moderate Comedonal and Inflammatory Acne Most cases of mild comedonal acne occur in teenagers and young adults, and these can usually be treated with traditional topical creams and gels. The most common of these are retinoids, like Retin-A, Differin, Renova, and Tazorac. They work by unblocking clogged pores. Dermatologists will often combine a topical retinoid with an oral antibiotic, such as doxycycline, tetracycline, minocycline or erythromycin, which kills the bacteria that cause inflammation around the blocked pores.