How does acne form?

Dr. Doris Day, MD
In all types of acne, the first step in the condition’s progression is a combination of increased oil production from the sebaceous glands and improper shedding of the skin cells lining the hair follicles. The skin on the face, chest, back, and upper arms all have an increased density of sebaceous glands, which are attached to the hundreds of miniature hairs that exit to the surface of the skin through follicles, commonly called pores.

Each follicle has a sebaceous gland attached to it. These glands produce an oily substance called sebum, which travels from the sebaceous gland through the follicle and ends on the surface of the skin. At the base of each follicle, a bacterium called Propionibacterium acnes (P. acnes) is also often present. This bacterium grows and flourishes under certain specific conditions, such as that of very low or no oxygen concentration. It is the main culprit that is responsible for a certain type of acne called inflammatory acne.

The upper layer of skin cells that line the follicle normally sloughs off at a regular interval of once every 1 to 2 months; the specific frequency of the sloughing varies depending on the site of the body in which the follicle is located. If the opening of the follicle gets blocked or if the skin cells of the lining regenerate either too quickly or too slowly and do not move up and out of the follicle properly, then problems arise. The next layer of skin cells behind them now have nowhere to go. Additionally, the oxygen supply in the follicle gets cut off, which then allows the P. acnes to grow and flourish.

The oil that the sebaceous glands produce, called sebum, as along with the protein that makes up the skin cells, serves as a perfect diet on which the P. acnes grow and prosper and produce more P. acnes. At this point the body recognizes that something is amiss and sends its army of white blood cells to survey the scene and attack as needed to clear the infection and rid the site of any foreign invaders. This leaves the skin looking red and bumpy and, often, feeling itchy or painful.

If the P. acnes is not activated, then the contents of the follicle build up and bulge behind the blocked opening and create a lumpy, bumpy look on the surface of the skin that can be white if the opening remains blocked or black if the contents finally burst through the to the surface and react with oxygen. These lesions are called whiteheads and blackheads, respectively. 

Find out more about this book: 100 Questions & Answers About Acne 

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