Normally as the body sheds skin cells, the keratinocytes rise to the surface of the skin. When someone has acne, the hair, sebum, and keratinocytes stick together inside the pore. This prevents the keratinocytes from shedding and keeps the sebum from reaching the surface of the skin. The mixture of oil and cells allows bacteria that normally live on the skin to grow in the plugged follicles and cause inflammation—swelling, redness, heat, and pain. When the wall of the plugged follicle breaks down, it spills the bacteria, skin cells, and sebum into nearby skin, creating lesions or pimples.Doctors and researchers believe that one or more of the following can lead to the development of acne:Excess or high production of oil in the pore.,Buildup of dead skin cells in the pore.,Growth of bacteria in the pore.The following factors may increase your risk for developing acne:Hormones. An increase in androgens, which are male sex hormones, may lead to acne. These increase in both boys and girls normally during puberty and cause the sebaceous glands to enlarge and make more sebum. Hormonal changes related to pregnancy can also cause acne. Family history. Researchers believe that you may be more likely to get acne if your parents had acne.Medications. Certain medications, such as medications that contain hormones, corticosteroids, and lithium, can cause acne.Age. People of all ages can get acne, but it is more common in teens.