Acne is the visible end result of hormonal, bacterial and inflammatory disturbances that take place at the level of the external skin surface. As the process advances, greater amounts of oil may be produced within the sebaceous glands, though the change in composition and quality of the oil may be more important than the quantity. The scale produced on the inside walls of the hair follicle becomes stickier, and it builds up and blocks the pore. This shows up as whiteheads and blackheads, or comedoes. The acne bacteria grow and multiply in the retained oil. The sebum acts as a nutrition source for the bacteria, which in turn releases chemicals within the pore. These alert and attract white cells from the blood, and that’s what leads to inflammation. On the skin, the inflammation is seen as pimples or zits, the scientific name being papules and pustules. As these inflamed hair pores and glands enlarge, the surrounding skin also becomes inflamed and may lead to even larger lumps and cysts. Inflammation may damage the cells that make collagen. Less collagen production causes thinning of the skin, which is seen as depressed scars. Occasionally, collagen production will increase, which then causes the scars to become thickened. Acne is mostly due to the combined effects of androgenic (male) hormones (testosterone and dihydrotestosterone), the acne bacteria, and inflammation of the oil gland. Other factors that may aggravate acne do so through the same mechanisms: increasing oil production, blocking the pores, and/or causing inflammation. When the skin surface and its pores are blocked, the pores are described as being occluded. Factors that may cause occlusion include certain cosmetics, oils, greases, and hairsprays. Hats, helmets and pads used in sports may also contribute to this problem as can humidity, sweating and the prolonged effect of contact with damp clothing. Certain hormonal medications that are androgenic in nature may aggravate acne by increasing oil production and pore blockage. Examples include anabolic steroids, and a component of the birth control pill called progestin. Other commonly used medications that may aggravate acne include lithium, and some anti-seizure medications.