Development Stages of Acne

Pimples usually seem to pop up overnight. This may sometimes be the case, but more often the pimple that you notice has taken weeks, even months to develop before you ever see it. Once it does appear, it might disappear in a day or two, or it could linger on for another few weeks or even months.

There are many different kinds of acne pimples, or lesions, as doctors call them. They can take the form of tiny skin-colored bumps, little white bumps, small red bumps, bigger red bumps, bumps with a black substance in them, pus-filled bumps, or even giant, painful ones. All of these are acne lesions, and all of them start out the same way: from a follicle that becomes blocked.

How Pimples Start

When shed epidermal cells start clumping together, along with the oily secretions and bacteria feeding on them, they begin to stick to the follicle wall. As more cells pile up, the wall grows thicker and it becomes more difficult for sebum to flow to the surface through the narrowed channel. The tube-shaped follicle starts to bulge a little as more and more shed cells stick to the growing mass inside it, and the opening to the surface becomes increasingly blocked. At this point, the problem is still a small one; you would need a microscope to see the plugged-up follicle.

Doctors call any stopped-up follicle a comedo (plural comedones), and a tiny microscopic one is called a microcomedo.  All acne pimples start out as microcomedones. Unfortunately, they don’t stay invisible. Eventually, thousands of dead epidermal cells build up in the follicle, and the plug makes the opening to the surface even smaller as it grows. The plug is not solid; it is more like a sponge. The skin cells in it are loosely clumped together, allowing oxygen and some amount of fluids to go in and out.

Meanwhile, the follicle starts to really bulge like a tiny balloon under the skin, because the sebaceous gland keeps producing sebum. Some of the sebum gets out to the surface, but most of it is trapped inside. Now the comedo is big enough to see if you look at yourself in the mirror.



When pimples are first visible, they appear as tiny white or flesh-colored bumps under the skin. They may be hard to see, but- if you stretch or pull your skin they become more evident. Because they are almost completely plugged, these acne lesions are called closed comedones. They are also known as whiteheads. Dermatologists sometimes call them “time bombs ” because they may not seem like much—they are only about 2 millimeters across, roughly the size of a pinhead—but they can develop into very serious kinds of pimples.


                          Closed Comedo

It is important to remember that the opening of the pore at the surface of the skin is not where the block occurs. It is down inside the follicle, so simple washing cannot clean the plug away. Often skin will grow over the pore, preventing almost all sebum from escaping and making the pore opening almost impossible to see.

Blackhead Stage

                   Open Comedo

Oil and dead cells continue to build up, and eventually one of two things will happen. Either the sebum will eventually force its way out to the surface of the skin, or it will put so much pressure on the follicle walls that they burst like a balloon that has too much air in it. If the pore eventually does open, it produces what is known as a blackhead or, in dermatological terms, an open comedo. People call it a blackhead because there is a gooey dark material inside.
The biggest misconception about blackheads is that the dark stuff is dirt and it is caused by not keeping the skin properly cleaned. The dark color is actually produced by a chemical reaction oi the sebum and dead cells with the oxygen of the air. The skin’s own melanin also makes a substantial contribution to the blackhead’s dark color. In fact, since melanin is produced only by the epidermal cells in the upper part of the follicle and not by those lining its lower part, the material in the open comedo is dark near the skin surface and lighter below. The color of blackheads also varies from one person to another, depending on the amount of melanin in the skin. Dark-skinned people tend to have very dark blackheads, while albinos have white ones. Since the matter in the comedo isn’t dirt, more frequent washing will not get rid of it. Neither will squeezing: Although some of the material near the surface will be forced out the narrowing of the follicle down below still remains, and the blackhead will eventually re-form.

From Bad to Worse

Annoying as blackheads may be, the alternative can be worse. The second outcome of a closed comedo—an exploded follicle wall—is a much more serious situation. For the first time, the acne process enters the body. (Remember, the follicle wall is really an extension of the outer layer of the epidermis, so in a way open comedones and even closed ones do not occur “inside” the body.) When the follicle wall is damaged, the dead cells and sebum flood into the dermis, along with some of the bacteria that were living in the follicle. This is when inflammation starts, and with it come redness and swelling.

Now the body’s defenses spring into action. When tissues are damaged, they send out chemical distress signals. A substance called histamine makes the microscopic capillaries dilate (widen), bringing more blood into the area. One side effect of this is that the capillary walls become leaky, and fluid from the blood oozes out into the surrounding tissues, producing swelling and inflammation. The chemical distress signals sent out by damaged tissues also summon white blood cells, which act as combination soldiers and garbage collectors. They are the body’s main line of defense against things that do not belong in it. Some of the white blood cells slip through tiny gaps in the capillary walls and move into the damaged tissues, prowling along the fluid-filled spaces between cells.

Soon the inflamed pimple is the scene of a fierce battle. White cells, looking like constantly changing blobs, creep through the tissues, homing in on bacteria, dead skin cells, or bits of sebum. The white blood cells flow over their prey, literally eating them. (The technical name of these germ-fighting white cells is phagocytes,which means “eating cells.”) The battle rages on as the white blood cells tirelessly gobble down bacteria and bits of dead matter. Some of these blood-cell soldiers are overcome in the fight, “slain” by doses of poison produced by the bacteria they have consumed. These dead blood cells, along with dead bacteria, sebum, and bits of skin-cell debris, accumulate in the form of the whitish matter called pus.

In the first stages of the battle, the increased flow of blood to the region of the damaged follicle makes the swollen area look red. Soon it becomes noticeable at the surface of the skin, in the form of a small red bump called a papule.


If there was only a small break in the follicle wall, the white blood cells will quickly win the fight and remove all the intruders within just a few days. The papule will disappear, and the follicle wall will be patched up with scar tissues. Sometimes the papules become hardened and remain for weeks before their contents are finally absorbed.

Often the damage is more extensive and cannot be contained right away. As the fight continues, a sac of pus forms, filled with oil and bacteria and white blood cells. At the surface, it looks like a yellowish or whitish cap on top of the red bump. It has now become a pustule.


The skin over the pustule is thin, and eventually it may open, so that the pus drains out; or the white blood cells patrolling the tissues may clean up all the pus and carry it away, digesting it as they continue their patrols through the body. Papules and pustules are what we normally think of as ”pimples.”

Battle Scars

When foreign material gets into the dermis and causes inflammation, some of the connective tissue is damaged. If all goes well, new tissue will form to replace the damaged tissue, and the skin will be as good as new. However, sometimes the repair is not complete, and a hole will be left in the dermis. Epidermis grows to cover the hole, and a depressed scar is formed.

Scarring is all the more probable when the break in the follicle wall is a large one. Then a lot of sebum, dead cells, and bacteria flood into the dermis, creating a large red bump, called a nodule. This is actually a larger form of the papule, and it feels firm. You may be tempted to squeeze it, hoping that the “bad stuff” will pop out and the pimple will heal. Instead, squeezing probably will just make the scarring worse.

The body’s defenses work hard to get rid of the irritating material of the nodule. After a painful flare-up that may last for up to a week or so, the nodule may gradually subside into a papule, which in turn may take some weeks to disappear. If the accumulation of bacteria and cell matter is very large, the contents of the nodule may become enclosed inside a makeshift wall below the skin surface. Now the lesion has become a cyst, which may grow to as much as an inch in diameter. Pus builds up inside the cyst, making it feel somewhat soft. It may be red and throbbing, an “angry-looking” boil. A cyst will heal faster if it is opened, so that the contents can drain; but this is definitely not a do-it-yourself project. Opening a cyst is actually surgery, and it should be done by a doctor or other medical professional with special precautions to stop the bleeding, prevent further infection, and minimize scarring.

When the acne process progresses to cysts, the inflammation is usually very serious. The sebaceous gland in these large lesions is destroyed, and oil will never be produced in that spot again. Cysts can be painful, and scarring often occurs, so you should see a dermatologist if your acne is this serious.


Many people never get papules, pustules, nodules, or cysts because their follicle walls are strong and the pore is always forced open, creating a blackhead, before the wall can give way. Other people almost never get blackheads but have a lot of inflamed lesions. This is because their follicle walls are not as strong. Unfortunately, there isn’t much you can do to strengthen your follicle walls. You can’t build them up with special exercises or salves or vitamins. Their strength is just something you’re born with. The same goes for scarring. Some people’s skin heals better than others’. Chance is also a big factor in scarring. If the follicle wall breaks close to the surface and if the break is small, there usually won’t be any scarring. But if it is a large break, deep in the dermis, chances are that scarring will occur.

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