Acne Anatomy
This section illustrates the process of the development of a whitehead and the unfortunate result of squeezing a pimple.
The birthplace of a whitehead is the pore around a hair follicle. Cells from the lining of the hair follicle are shed and clump together blocking the sebum, (which normally lubricates the skin), from exiting the pore to the skin surface. When sebum is blocked in the pore but is exposed to air, a "blackhead" forms.

The main components of a whitehead are the hair follicle where dead cells accumulate, the sebaceous gland, which makes oil or sebum, and the skin surface…where the effects of what is happening under the surface…are visible to you.

When the outlet for the hair follicle is closed, the sebum and dead skin cells begin to build. Bacteria that normally live on the surface of the skin also mix with the dead skin cells and sebum causing infection.

You see this infection as swelling, redness and pus. And while you may feel like what you see on the surface is unsightly, the real damage can be happening underneath.

When you squeeze an infected pimple, you create pressure that can spread the infection.

The infection spreads above the skin, but also deep inside the pore. This enlarges and spreads the infection, and can cause or increase scarring.

When the damage is severe enough, scar tissue forms, which appears as a depression, or "pit" in the skin surface.

Scarring is the long-term effect of acne and may look like an uneven skin surface, or in some skin tones, discoloration.

Excerpt from www.healthseekers.com