How It Happens
Acne is not your fault. It is now understood that genetics play a role in acne. If your parents had acne as teenagers, you most likely will too.
Acne usually begins around puberty, when males and females experience fluctuating hormone levels. These hormones regulate the activity and size of the oil-producing (“sebaceous”) glands found inside the pores of the hair follicles within the skin. The elevation of these hormones causes the oil glands to expand, in turn triggering an over-production of oil.
The sebaceous glands make an oily substance called “sebum”. During the skin's natural cycle, sebum travels through the hair follicles to the surface of the skin. The lining of the follicle wall then sheds skin cells, which stick together with the sebum. When the skin is over-producing and shedding skin cells at the same time, the follicle gets clogged, blocking the opening on the skin's surface. When the plug gets big enough to push to the skin's surface and be seen, it's officially a blackhead or whitehead. Additionally, the sebum and cell debris together contribute to the growth of bacteria that live inside your pores causing infection, pain, redness and swelling. These blemishes can be painful and may cause scarring.
Your own body will naturally attempt to clear the clogged pores by sending in certain specialized cells that invade the follicle to help clean it up. However, in the process, the wall of the follicle may weaken and rupture, emptying the contents of the follicle into surrounding tissue. When this occurs, swelling or redness can develop around the affected follicle, resulting in the larger bumps or pimples characteristic of acne. These are known as papules (red bumps) and pustules (yellowheads) and can sometimes cause scarring.
From the time acne begins to form under the skin until its disappearance, the life cycle of a pimple can take 8 to 12 weeks to run its course. And it can take even longer for the darkened spots left by some blemishes to fade away completely.