Acne occurs when the pores become clogged with oils, dead skin cells, or bacteria. When the pores get clogged, it becomes impossible for the natural skin oils to drain to the surface and causes a bump. There are several different types of acne , and how the pimple is formed influences how it will look and essentially what type of acne it is.
A whitehead (seen in the photo to the left) is formed when the pore becomes clogged, but the trapped oils and bacteria stay beneath the surface of the skin. This causes the skin over that pore to stretch, turning it white. Sometimes they are virtually invisible to the naked eye, and sometimes they are blatantly obvious. After a period of time, the whitehead may rupture, release its contents to the surface, and eventually heal. With the assistance of an acne medication, these whiteheads will disappear more quickly and be less likely to leave scars.
A blackhead is initially formed the same way as a whitehead, but the oils and bacteria spill onto the surface of the skin during its formation and oxidize. This gives you a blackish-brownish bump that will misleadingly look like dirt. A blackhead cannot simply be washed away though. It ruptures similarly to a whitehead and will eventually heal. As with whiteheads, scars can be prevented with the appropriate acne medication and the healing may move along more quickly.
While both whiteheads and blackheads are considered non-inflammatory because of their fairly un-intrusive nature, papules and pustules are considered inflammatory because they are typically sore and inflamed. Papules are the first sign of a pimple and appear as small, red, raised bumps; they are caused when the side of the follicle wall breaks. A papule is a signal that there is an infection beginning in the hair follicle. Papules then develop into pustules, which are what we commonly know as a ‘pimple’ or ‘zit’. Pustules are red, tender, raised bumps with white pus inside them. Pustules have been known to burst after a period of time, and can leave scars if the appropriate acne medication is not used.
Two other types of inflammatory acne are nodules and cysts. Nodules are large painful lumps that form beneath the surface of the skin. They are caused when the bottom of the follicle wall collapses, causing the pore itself to collapse. When the oils and bacteria build up within the pore, a nodule is created. Cysts are painful bumps that also occur beneath the skin, but are filled with pus. Cysts have been known to burst after a period of time and both cysts and nodules can leave scars.
The last type of acne is called milia. It is simply a spread of white bumps, usually across the nose or forehead, caused by dead skin cells trapped under the top layer of skin. While milia can last for a very long time, it will typically resolve itself. Acne medication can speed along the healing process and prevent scars.