Acne is the result of excess sebum (oil) production during the increased hormone levels of early puberty; in particular, androgens (male hormones) cause the sebaceous (oil-producing) glands to grow larger and produce more oil. Typically, this oil flows up through the pore and is evenly distributed on the skin’s surface. Although not entirely sure what purpose sebum serves…, scientists currently believe that its part of the immune system’s protection of the skin.
Unfortunately, excessively high sebum levels irritate the pore and cause it to undergo hyperkeratinization, or hardening. Scientists have recently found reason to believe this irritation may be due to a deficiency of linoleic acid caused by the excess sebum. I have not yet heard of a linoleic acid based acne medicine, but it’s an exciting prospect for the future because all acne begins with hyperkeratinization and formation of a microcomedo, or hyperkeratotic pore.
If the top of the pore closes, the microcomedo becomes a whitehead; if the top of the pore stays open, it becomes a blackhead. Since whiteheads are closed, they become a breeding ground for acne bacteria that can’t survive in the presence of oxygen; furthermore, as more oil and keratin enter the whitehead pressure builds, sometimes causing the pore wall to rupture. When the pore ruptures, its contents spill into the surrounding tissue initiating an inflammatory response with accompanying symptoms of redness, swelling, and pain; thus, only whiteheads become inflammatory acne, manifesting as pustules, papules, or cystic-type acne.
You can probably confirm these statements from personal observation, since you’ve probably noticed that blackheads aren’t usually red, swollen, or painful. The open pore of the blackhead doesn’t allow acne bacteria to grow rapidly; furthermore, the open pore allows material to escape periodically avoiding a build-up of pressure and subsequent rupture.
But why do blackheads usually occur on the nose? And, why do they take so long to get rid of?
Blackheads are unique in their localization on the nose. The nose has one of the highest concentration of sebaceous glands on the entire body; furthermore, the nose has relatively large pores compared with the rest of the body. The high concentration of sebaceous glands leads to high levels of sebum making many pores on the nose susceptible to acne at the same time, and the large pores of the nose cause most microcomedos to stay open at the top, leading to blackheads.
Based on my reading of Albert M. Kligman’s, M.D., Ph.D., 1974 seminal article “Overview of Acne”, I believe that blackheads take longer to get rid of because they cause less damage to the pore than inflammatory acne. In inflammatory acne, the sebaceous glands and other structures of the pore deteriorate, and the immune system liquefies the material inside so that it can be expelled from the pore. You’ve probably noticed this process: an acne papule that was firm but after several days was easy to pop. At this point, the pore basically “starts over”. Since blackheads don’t become inflamed, the structures remain largely intact so that you can squeeze and expel the material, but the pore remains keratotic, or essentially an empty-blackhead that will soon fill again. In order to remedy this situation, you’ll need a medicine that helps regulate hyperkeratinization like the topical retinoids: adapalene, tazarotene, or tretinoin.