sebum becomes oxidized, turning dark in color. There are many types of inflammatory acne. The two most common are papule acne, which occurs when a pore becomes inflamed; and pustule acne, which occurs when white blood cells make their way to the surface of the skin. Pustule acne is the most common type, and is what people refer to as “zits.” Milia acne occurs when dead skin cells get trapped in pores.