Acne or acne vulgaris (vulgaris meaning common) is a chronic skin condition that is characterised by spots which typically form over oily regions of the body (face, chest, neck and back). The lesions form around hair follicles and their associated oil-secreting glands known as pilosebaceous units. Acne can present in many different forms including blackheads (open comedomes), whiteheads (closed comedomes), papules (lesions of solid skin elevation) and pustules (lesions containing pus).
Sebaceous glands secrete sebum an oily substance that acts to lubricate the hair follicle and skin. Sebum helps with body temperature regulation and aids the skins barrier function by acting as a natural antimicrobial. Hormones influence sebum production, with male sex hormones (androgens) increasing production and female sex hormones (oestrogens) decreasing production, environmental temperatures can also alter sebum characteristics. In normal function, sebum travels up the hair follicle with the hair shaft and out of the pore onto the skin. Excessive skin keratinisation is also seen in acne, again this process is hormone mediated causing excessively rough hair follicles which are prone to sebum plugging. In acne, sebum and skin debris build up in the pore disrupting sebum secretion, if debris builds up but still remains open blackheads (open comedomes) are formed and if the pore completely blocks whiteheads (closed comedomes) are formed. In more severe cases the wall of the hair follicle may burst due to the blockage causing inflammation. Commensal bacteria (normal bacteria that live on the skin) can then breach the skins barrier causing localised infection further exacerbated swelling, redness and pain. In the most severe cases of acne, this process leads to irreversible scarring of the skin.
There are multiple independent factors that can exacerbate the above process including the application of cosmetic products to the skin, diet, humidity, stress and medications taken for other health issues.
Treatment of acne can be broken down into three broad categories; treatments that prevent initial plugging of the hair follicle, products that unplug blocked follicles and products that prevent or diminish the subsequent inflammatory and scarring processes.
Preventing hair follicle plugging.
Initial plugging occurs due to increased sebum production and skin keratinisation/skin debris formation. Hormones specifically male sex hormones (androgens) drive both of these processes so drugs that moderate androgen production can be useful preventative treatments examples include the combined oral contraceptive tablet, lymecycline, roxithromycin and ketoconazole. Retinoids are another broad group of medicines which have multiple beneficial actions including normalising skin keratinisation (reducing follicle occlusion) and increasing skin turnover (pushing follicle plugs out).
Unplugging blocked follicles.
Removal of excessive sebum and dirt accumulation from hair follicles through regular use of skin cleansers can be an effective means of acne prevention. Benzyl peroxide is a common acne medicine which acts by breaking down the keratin in the follicle plug. Other drugs alter skin growth cycles to unplug pores including retinoids (as mentioned above) which speed up skin proliferation and salicylic acid which facilitates shedding of dead skin.
Preventing inflammation and scarring.
Inflammation in acne is driven by the skin's reaction to tissue damage and localised infection. Treatments that suppress inflammation include steroids and non-steroidal anti-inflammatories (ibuprofen). Killing bacteria can occur both by the use of antibiotics both topically (cream-based) or orally (tablets), or through the use of other agents that create hostile environments for bacteria to survive in.