Acne forms over the course of several weeks and through a series of complex events in the skin. The pimple that you see on your chin as if it appeared overnight, has in fact been hard at “work” below the surface of your skin for weeks before you see it. Below I’ll describe the entire process of how acne forms.
Acne begins its life in the hair follicle or pilosebaceous unit. This unit consists of the hair follicle itself and an attached sebaceous gland which produces sebum or oil. There are three types of hair follicles: vellus, terminal, and sebaceous. In the first two types of follicles the hairs (though at different stages of development and appearance) fit closely into the follicles which is to say that the diameter of the growth channels are the same as the hairs themselves. Because of this tight fit there isn’t room for debris or sebum to remain in the follicle and subsequently form a pimple. But what then happens in the sebaceous follicles? The hairs in those follicles are small and frail leaving more than enough room for debris and sebum to accumulate and get stuck there. These sebaceous follicles are concentrated on the face, neck, shoulders, upper chest, and back subsequently explaining why these are the areas where people experience breakouts. Furthermore, these follicles are largest and most numerous on the face.
People who are prone to acne tend to produce abnormal amounts of sebum; this production of sebum is triggered by hormones known as androgens. There are different types of androgens but the significant one in terms of acne breakouts is testosterone which circulates in the body via the bloodstream and reaches the hair follicles that way. In the hair follicle an enzyme changes the testosterone into a chemical called dihydrotestosterone, or DHT for short, which then signals the sebaceous glands to start producing sebum. Just because you suffer from oily skin or acne does not necessarily mean you suffer from a hormonal imbalance or an overabundance of DHT. Typically it just means that your sebaceous glands are very sensitive to the above mentioned hormones and then your oil production becomes excessive.
Yet even if you have oily skin you might never breakout and even people with dry skin can breakout. So how does that happen? The main cause of acne are comedones or blocked pores. The pores or openings that lead down into the sebaceous glands are the issue here. Comedones are formed when something goes wrong with the skin cells lining the follicular channel. If the skin processes are working normally then the sebaceous glands are continually expelling dead skin cells or keratinocytes onto the surface of the skin along with the normal flow of sebum. But this process can malfunction and two things can happen – the follicle can actually step up its production of keratinocytes thus creating a huge amount of debris or dead skin cells and then secondly, that excess amount of cells stick together much like if they were cement. So instead of leaving the follicle as they should these dead cells remain where they are and mix together with the sebum already in the follicle. This produces a microcomedo. Doctors call these microcomedones “precursor lesions” to acne, and if you suffer from acne your skin is full of them. The microcomedones take about six to eight weeks to form and by the end of that time period enough dead cells and oil have accumulated in the follicle in order to produce a closed comedone which feels like small bumps on your skin (you can see them as well). This closed comedone can mature into what is known as an open comedone or a blackhead. As it grows the comedone presses the pore open at the surface, and then the accumulated oil and dead cells oxidize turning black. Some sources say that the skin pigment melanin is what accumulates at the top of the pore and turns black. Blackheads can grow to anywhere between 2 to 5 millimeters and remain in place for months and even years. Inside the follicle of a blackhead cell production slows down considerably and the sebaceous glands all but stop secreting oil. Another form of a comedone is a whitehead which like a blackhead in that the pore is filled with oil and dead cells. But unlike a blackhead the accumulation takes place beneath the surface of the skin and the mixture of materials does not oxidize. People who have what is called non-inflammatory acne suffer from a mixture of whiteheads and blackheads and rarely form the red bumps most people associate with acne.
Having now explained non-inflammatory acne it is time to explain inflammatory acne. This type of acne is characterized by pimples, papules, pustules, nodules, and cysts. Inflammatory acne is caused by a rod-shaped bacteria called Propionibacterium acnes or P. acnes for short. This bacteria thrives in places without oxygen and as such is found deep in the skin which explains why many acne products cannot destroy this persistent and tough bacteria. P. acnes multiplies quickly inside closed comedones and additionally excretes chemicals that damage the lining of follicle. In addition to this damage these toxic chemicals attract the attention of the body’s immune system which seeks to destroy the bacteria. It is at this point that one feels a slight elevation under their skin and/or a tenderness. The P. acnes find their targets in the follicles and release enzymes which destroy part of the follicle’s wall creating a rupture or break. Sometimes the body repairs the break quickly and what might have been a major pimple in the making does not occur. Other times the rupture will become a papule – a raised, red spot without a visible head. The redness of the papule comes from a network of blood vessels, and the swelling is caused by lymph and other fluids.
If the body does not repair the follicular rupture quickly then the contents of the follicle spill out into the surrounding tissue. The contents of follicle include sebum, hair, bacteria, and skin cells. The body then sends neutrophils to the area to isolate and destroy the foreign materials. As they go about their job the neutrophils destroy more of the follicle wall and the surrounding tissues’ dermis. This activity will produce a pustule or a white or yellow capped acne lesion filled with pus. The pus contains white blood cells, bacteria, and other debris. Eventually the top of the pustule breaks and the pus escapes taking along with it the remnants of comedone. Sometimes this could be the very end of the pimple, but if bits of material are left behind another pimple could form in exactly the same spot and so the cycle of breakouts continues.
Nodular or cystic acne is most severe type of acne. It consists of large, painful, and solid acne lesions that are lodged very deep in the skin with only a small opening to the surface of the skin where the follicle exits the skin. They can feel hard to the touch, and these lesions can last for months leaving behind crater like scars when they finally heals.
Now that you have a better understand of how acne forms you can determine how to treat your acne is a more effective manner. The two keys to treating acne are unclogging pores and killing the acne bacteria. Gentle and regular exfoliation can help unclog your pores, and benzoyl peroxide can kill the acne bacteria.
Sources and Further Reading
- Most of the information in this post I learned from Lydia Preston’s book Breaking Out – chapter 3
- 100 Questions About Acne by Dr. Doris Day is another good resource