Oral contraceptives high in progesterone can cause breakouts, too. The sebaceous glands, located in each hair follicle or tiny pit of skin, produce oil that lubricates the skin. Sebaceous glands are found in large numbers on the face, back, chest, and shoulders. If some of the oil becomes trapped, bacteria multiply in the follicle and the skinbecomes inflamed. Several of these spots can come and go over a period of months or years.
Blackheads form when sebum combines with skin pigments and plugs the pores.
If scales below the surface of the skin become filled with sebum, whiteheads appear. In severe cases, whiteheads build up, spread under the skin, and rupture, which eventually spreads the inflammation. The exact cause of acne is not known, but factors that contribute to the condition include heredity, oily skin, and androgens. The skin is the largest organ of the body. One of its functions is to eliminate a portion of the body's toxic waste products through sweating.