What Causes Acne?

Top 3 Factors that Cause Acne

There are three major factors that cause acne to develop: over-active sebaceous (or oil) glands, abnormal shedding of dead skin cells, and a proliferation of acne-causing bacteria. None of these factors have to do with skin care or lack thereof, and they all must be present for acne to occur.

The tendency to develop acne has more to do with genetics than anything. You develop acne because your skin has the propensity to develop acne; it's nothing you did or did not do.


Overactive Sebaceous Glands

Trapped oil within the pore causes blockages and blemishes. Photo: Eric's Phtotgraphy / Getty Images

Sebaceous glands are tiny glands that reside in our skin. Their job is to create sebum, or oil, that's needed to lubricate the skin's surface.

People who are prone to acne have oil glands that produce more sebum than is necessary. Excess oil remains in the pore, blocking the sebaceous duct and creating a blockage within the follicle. This blockage is called a comedo. 

Comedones (the plural of comedo) are the starting point for all acne blemishes, from the tiniest of blackheads to larger, inflamed papules and cystic breakouts.

Interestingly, there's some indication that the sebum of those who have acne may also be different in its makeup. People with acne tend to have sebum with higher levels of squalene and wax esters than those without acne. They also have lower levels of free fatty acids and linoleic acid in their sebum.

It's theorized that this composition creates a more favorable environment for acne-causing bacteria. Basically, it makes for a better home for the bacteria that are responsible for inflamed acne breakouts.


Abnormal Shedding of Skin Cells

Skin layers
Images: BSIP / UIG / Getty Images

The top layer of skin, your epidermis, constantly sheds away dead skin cells through a process called desquamation. Consider this the natural way the skin exfoliates and renews itself.

The epidermis itself is made up of several layers. New skin cells are created in the stratum germinativum, which is the deepest layer of the epidermis. 

These new cells slowly travel up through the epidermal layers until they reach the outermost layer, called the stratum corneum. Once they reach the stratum corneum, the cells have flattened and dried out. Essentially, the skin cells are "dead." 

These dead skin cells continually fall away from the stratum corneum and are replaced by new cells pushing up from below. You are constantly shedding dead skin cells. In fact, most of the dust in your home is made up of dead skin.

In acne-prone skin this desquamation process goes awry, with four to five times more skin cells being produced than in normal skin.

There are also less Lamellar granules in the skin of people prone to acne. Lamellar granules are found within the cells of the stratum corneum. They are responsible for releasing enzymes that digest the substance that that holds cells together.

Simply speaking, acne-prone skin produces more dead skin cells than is typical, and those skin cells are not being shed properly. Instead, the cells remain suck inside the follicle creating a blockage.


Proliferation of Bacteria

Propionibacteria acnes
Photo courtesy of the CDC

Propionibacteria acnes (P. acnes) are bacteria routinely found on most skin. In those with acne the P. acnes population grows out of control.

When a pore is clogged by dead skin cells and sebum, it creates an anaerobic environment: oxygen can't get into the pore. P. acnes just happen to thrive in this environment, so their population grows quickly within a plugged pore.

The P. acnes digest the oil trapped within the pore, producing a fatty acid waste. This waste irritates the pore lining, causing redness,inflammation, and when white blood cells rush in, pus. Suddenly, you have a zit.

It is important to know that cleansing cannot wash P. acnes away. Its presence does not point to a lack of hygiene in any way.

A Word from Verywell

You may be surprised to see that certain things didn't make this list, things like diet or lack of cleansing or touching your face. So many things that we assumed caused acne really don't have much effect on the skin, and are more myth than fact.

Although your skin may be prone to breakouts, you're not stuck with them. There are plenty of treatments available that can help treat these major acne-causing factors, allowing your skin to clear up and heal.

Over-the-counter acne products can be helpful if you have minor blemishes. But if your acne is more severe, inflamed, or you've tried OTC products without luck, give a dermatologist a call. There are plenty of prescription acne medications available that can help. With the right medications, you will be well on your way to clear skin.

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