What is acne?
Acne is one of the most common diseases in the world, and it affects approximately 650 million people worldwide. It is also the eighth most common disease in humans. Although it is not a life-threatening disease, it is concerning to those who suffer from it, as it can cause significant psychological distress and affect people for many years. In fact, according to a 2005 article in The New England Journal of Medicine,
“Studies suggest that the emotional impact of acne is comparable to that experienced by patients with systemic diseases, like diabetes and epilepsy.”
Acne, also commonly known as “pimples” or “zits”, is actually a broad term that encompasses a variety of skin conditions that affect the pilosebaceous unit (the skin structure consisting of the hair, hair follicle and oil gland). It is a myth that acne is a condition of adolescents; in fact, adult acne is common and for some, acne can persist into their 50s. Acne usually affects the face but may also be found, or be even more persistent, on the back, neck and chest.
Why do I have Acne?
There are 4 major factors that affect the pathogenesis (development) of acne. Each individual’s acne is different due to a complex interplay of these 4 factors.
Increased Sebum Production
The sebaceous (oil-producing) glands of people who get acne are particularly sensitive to blood levels of certain hormones, which are present in both men and women. These hormones cause the glands to produce an excess of oil. The hormones involved are mainly the androgens (DHEA-S, testosterone); recently, scientists have discovered that corticotrophin-releasing hormone (CRH), one of the hormones involved in the stress response, has activity on the human sebaceous gland as well.
At the same time, the dead skin cells lining the pores are not shed properly in people who are prone to acne, and these dead skin cells clog up the follicles. These two effects result in a build-up of oil, producing microcomedos (including closed comedones (whiteheads) and open comedones (blackheads)), which are the precursors of frank acne vulgaris.
The acne bacterium (known as Propionibacterium acnes) lives on everyone’s skin, usually causing no problems, but in those prone to acne, the build-up of oil creates an ideal environment in which these bacteria can multiply. In fact, the bacterium utilizes triglycerides (lipids) in our sebum as a nutrient source (its food!). This triggers inflammation and the formation of red or pus-filled spots.
Immune Response Triggered Inflammation
The proliferation of P. acnes bacteria causes the body to produce an immune response of inflammation to kill the bacteria and heal the skin. Differences in each individual's inflammatory response to P. acnes contribute to the variation in the prevalence and severity of acne. It is also the inflammatory process that leaves the skin with a blemish or mark, known as post-inflammatory hyperpigmentation (PIH), and/or a scar.
In addition, a 5th factor for acne, which is explained to certain patients, will be the presence or co-existence of certain internal medical problems. Conditions which are associated with acne include polycystic ovarian syndrome, congenital adrenal hyperplasia, and adrenal gland and ovary cancers. Certain types of acne can also be caused by or worsened by medication given for other conditions. These may include corticosteroids, contraceptive pills/injections, hormonal medications and medications for conditions such as seizures, bipolar disorder and tuberculosis, among many others.