How does a pimple form?

The whiteheads, also known as closed comedones or microcysts are a form of sub-surface pre-acne. They result from an over-secretion of sebum by the sebaceous glands. This excess sebum will block the pores, forming a micro-lesion with a white appearance.

Beyond hyperseborrhea, whiteheads also result from hyperkeratinization of the cells in the follicular canal wall. In other words, the cells multiply excessively, leading to a blockage of the follicular canal that prevents the elimination of sebum.

Thus, sebum accumulates under the skin and gives rise to a localized and hardened bulge in the skin. Whiteheads can spontaneously regress or become inflamed. They are frequently observed in retentional acne.

Note : there are also open comedones, but these are not considered pimples. The open comedones or blackheads result from the same process as microcysts. When these clogged pores are open, oxidation occurs upon contact with air and the impurities trapped inside the pore darken, thus forming a blackhead.

The papules are inflammatory skin elements characterized by a swelling with a solid consistency, that is to say containing neither liquid nor pus, of small size (ranging from 1 to 4 mm) and of a pink to red color.

Papules are one of the manifestations observed ininflammatory acne. This inflammation is caused by a bacterium: Cutibacterium acnes.

Cutibacterium acnes is a commensal bacterium of the skin microbiota. It contributes to the maintenance of healthy skin balance. However, under certain conditions, Cutibacterium acnes proliferates abnormally and becomes pathogenic.

As mentioned earlier, microcysts, which are the least severe manifestation of acne, can become inflamed. Indeed, microcysts are caused, among other things, by an excess of sebum. This fat-rich environment promotes the proliferation of Cutibacterium acnes, which secretes inflammation mediators. This triggers an inflammatory response on the skin's surface. This bacterium is also responsible for a hyperkeratinization of the skin (thickening of the skin) which promotes the appearance of blemishes.

The papules observed in inflammatory acne are indicative of a superficial inflammation caused by the proliferation of Cutibacterium acnes.

The pustules are small inflammatory lesions of the skin characterized by a well-defined and circumscribed elevation of the epidermis (diameter less than 5 mm) and topped in their center by a purulent liquid of white color or yellow.

Just like papules, pustules are observed in inflammatory acne and are a sign of superficial inflammation.

When inflammation is too severe or lasts too long, a bacterial contamination comes to infect the pimple which will then fill with pus. In this case, the papule turns into a pustule.