Your pores produce an oily substance known as sebum, which is secreted by small sacs called “sebaceous glands”, sprouting off pore walls deep within your skin. As sebum flow increases, pores must open wider, so the mouth of the pore appears larger at its opening on your skin’s surface. Driving sebum production are the hormones progesterone and testosterone, both of which are stronger during your teens and often into your 20s, 30s and sometimes beyond. These hormones kick sebaceous glands into high gear. When groups of sebum-releasing pores collect in one spot, skin takes on a greasy, “orange peel” look.