Acne is an inflammatory disorder of the skin, more specifically of the hair follicles, characterised by the emergence of superficial acne lesions ( comedones, papules and pustules ) or deep ones (nodules and cysts ). This condition is very common among teenagers, but also occurs in some adults. It primarily affects areas rich in sebaceous glands, such as the face, upper back, chest, neck, shoulders, etc...
Acne is the result of several interlinked factors. It all begins with either an excessive production of sebum, or a thickening of the wall of the sebaceous gland duct (which connects the follicle to the skin surface), thereby narrowing its diameter and partially blocking the diffusion of sebum out of the sebaceous gland. In other cases, acne can be induced following a hyperkeratinisation (poor evacuation of dead cells), thus trapping the sebum in the follicle. This seborrheic retention is responsible for the formation of comedones (blackheads and whiteheads).
Indeed, this fat-rich environment can lead to the abnormal proliferation of a pathogen, Cutibacterium acnes (formerly listed under the name Propionibacterium acnes), on the skin surface and in the hair and sebaceous follicles. This abnormal multiplication of the bacterium Cutibacterium acnes, usually well tolerated by the skin, triggers the secretion of pro-inflammatory factors. The resulting inflammation can also be due to damage caused by the follicle. At this stage, papules or nodules may form. However, the follicle can subsequently be superinfected by other microorganisms present on the skin. This can then lead to the appearance of a pustule or a cyst containing pus.
Acne is linked to multiple origins:
The hormonal fluctuations (during puberty, a few days before menstruation, during pregnancy, at the time of menopause);
The genetics (family history);
Certain medications (oral contraceptive treatment, cortisone derivatives, certain antibiotics, lithium, certain antidepressants, antiepileptics, immunosuppressants);
Theuse of comedogenic cosmetics ;
The stress (production and release of Substance P by nerve cells, which can influence sebum production);
The repeated friction on a specific area of the skin.
Once healed, acne can leave temporary or permanent scars (brown spots), especially when the acne has been particularly severe.