All acne is a disorder of the pilosebaceous unit, which is made up of a hair follicle, sebaceous gland, and a hair. These units are found everywhere on the body except on the palms, soles, top of the feet, and the lower lip. The number of pilosebaceous units is greatest on the face, upper neck, and chest. Sebaceous glands produce a substance called sebum, which is responsible for keeping the skin and hair moisturized. During adolescence sebaceous glands enlarge and produce more sebum under the influence of hormones, also called androgens. After about age 20, sebum production begins to decrease.
Acne & Bacteria
A bacteria, known as Propionibacterium acnes, is a normal inhabitant of the skin. It uses sebum as a nutrient for growth, therefore increases in follicles during puberty. People with acne have more Propionibacterium acnes in their follicles than people without acne. The presence of bacteria attracts white blood cells to the follicle. These white blood cells produce an enzyme that damages the wall of the follicle, allowing the contents of the follicle to enter the dermis. This process causes an inflammatory response seen as papules (red bumps), pustules, and nodules. The bacteria also cause the formation of free fatty acids, which are irritants, increasing the inflammatory process in the follicle.
Normal Follicles
Sebum produced by the sebaceous gland combines with cells being sloughed off within the hair follicle and "fills up" the hair follicle. When the follicle is "full", the sebum spreads over the skin surface giving the skin an oily appearance. When this process works correctly, the skin is moisturized and remains healthy.
Obstructed Follicles
Problems arise when the sebum is trapped in the hair follicle। For reasons that are still unclear, some hair follicles become obstructed. The sebum is produced but gets trapped on the way out, and the cells that are normally sloughed off become "sticky", plugging up the follicle. The process of obstructing follicles is called comedogenesis. It causes some follicles to form a type of acne called comedones, also known as blackheads and whiteheads.
What Causes Acne?
There are four major factors responsible for causing acne. They act together to cause the characteristic pimples, whiteheads and blackheads associated with acne. They are:
Overactive Oil Glands
Oil glands are located deep in the skin. They are also known as sebaceous glands.
- Each oil gland is connected to a tiny canal that contains a hair. The canal with its contained hair is called a follicle.
- The glands produce oil (also known as sebum) that flows to the surface of the skin through these canals to lubricate the hair follicles and the surrounding skin.
- The opening of the canal with the attached hair (follicle) onto the skin is the skin pore.
The oil glands vary in size, and the larger ones are associated with visible skin pores.
The oil glands are stimulated to produce oil by hormones, specifically the male hormones called androgens (women also have these hormones, but much less of them). These hormones are produced by the testes in men and by the ovaries in women. In both sexes, androgens are also produced by the adrenal glands.
During times of stress, the adrenal glands produce increased levels of these hormones, causing even greater enlargement of the oil glands.
During puberty, the oil glands become overactive in response to hormonal changes.
Blockage Of The Skin Pores
Oily skin occurs when an overactive oil gland enlarges and overproduces oil. Acne develops when some of the pores (through which oil normally flows from the oil gland to reach the skin surface) become blocked, resulting in trapping of oil within the skin pores.
The pores are blocked by skin cells that have been shed from the lining of the skin pore and have bunched together. The cause for this clogging is not known, but it is not due to poor hygiene. A blackhead or whitehead will develop from this skin pore blockage
Activity Of Normal Skin Bacteria
Although acne is not caused by a bacterial infection, bacteria do play a role in making the situation worse. The bacterium
When oil is trapped in the hair follicles, the normal skin bacteria P. acnes will grow in the blocked pore. The bacteria produce chemicals that alter the composition of the oil, which makes it more irritating to the skin and causes inflammation.
Inflammation
Inflamed skin is characterized by redness, swelling, warmth and discomfort. Inflammation of the skin occurs because the body's immune system is acting to rid itself of a foreign substance. In the case of acne, this substance is either bacteria or the irritating compounds they have produced.
These four factors contribute to blocked skin pores, which bulge outward to form:
- Blackheads. These form when the pores are clogged close to the surface of the skin. Because they are exposed to the skin surface, blackheads don't usually become inflamed. Blackheads are dark due to the presence of a dark
pigment . This color is not the result of dirt in the pores. - Whiteheads. These develop from a blockage deeper in a pore. Lacking a drainage path, the oil accumulates in the skin, causing small flesh-colored or white-colored bumps. Unlike blackheads, whiteheads are more likely to lead to the red inflammations known as pimples or zits.
- Pustules (also known as pimples or zits) occur when the walls of the blocked follicle ruptures. Oil, dead skin cells, and bacteria normally found on the skin surface get into the skin and irritate it, forming small areas of inflammation.
- Cysts are larger, red, inflamed areas deep in the skin that indicate a more extensive infection.
