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How Do Pimples Form?

Pimples can appear on the face or body, particularly on the back, chest, or buttocks. One of the main causes of pimples is acne. There are different types of acne, and therefore different types of pimples. Then, a question arises:  How do pimples form? Find out in this article.

Published February 29, 2024, by Sandrine, Scientific Editor — 7 min read

A Few Words About Acne.

Acne is an inflammatory skin disease of the pilosebaceous follicle. It is the most common dermatosis, and the number one reason for consulting a dermatologist. It generally affects teenagers at puberty, but can also occur in adulthood.

There is no single cause of acne, but several. However, three main elements are important in the pathophysiology of acne: excess sebum, the Cutibacterium acnes bacterium and hyperkeratinization.

There are numerous types of acne pimples: whiteheads, papules, pustules, nodules, and cysts. At the skin level, these do not form in the same way. Let’s take a look at the process of a pimple in its variations.

How Do Whiteheads Form?

Whiteheads, also known as closed comedones or microcysts, are a form of sub-superficial pre-acne. They result from hypersecretion of sebum by the sebaceous glands. This excess sebum blocks the pores, forming a white microlesion.

In addition to hyperseborrhea, whiteheads also result from hyperkeratinization of the cells lining the follicular canal. In other words, the cells multiply excessively, leading to obstruction of the follicular canal and preventing sebum elimination.

As a result, sebum accumulates under the skin, giving rise to an indurated, localized bulge. Whiteheads may regress spontaneously or become inflamed. They are frequently observed in retentional acne.

Note: There are also open comedones, but these are not considered pimples. Open comedones or blackheadsresult from the same process as microcysts. When these clogged pores are opened, oxidation occurs on contact with air and the impurities trapped inside the pore turn brown, forming a blackhead.

How Do Papules Form?

Papules are inflammatory skin elements characterized by a swelling of solid consistency, i.e., containing no liquid or pus, small (1 to 4 mm) and pink to reddish

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

Cutibacterium acnes is a commensal bacterium of the cutaneous microbiota. It helps maintain the skin's equilibrium. However, under certain conditions, Cutibacterium acnes proliferates abnormally and becomes pathogenic.

As mentioned above, whiteheads, which are the least severe manifestation of acne, can become inflamed. In fact, they are caused, among other things, by excess sebum. This grease-rich environment encourages the proliferation of Cutibacterium acnes, which secretes inflammatory mediators. This generates an inflammatory response on the skin's surface. This bacterium is also responsible for hyperkeratinization of the skin (thickening of the skin), leading to the appearance of blemishes.

The papules seen in inflammatory acne are the sign of superficial inflammation caused by the proliferation of Cutibacterium acnes.

And What About Pustules?

Pustules are small inflammatory skin lesions characterized by a well-defined, circumscribed elevation of the epidermis (less than 5 mm in diameter), with a white or yellow purulent fluid at the center.

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

When the inflammation is too great or lasts too long, bacterial contaminationinfects the pimple, which fills with pus. In this case, the papule becomes a pustule.

How Do Nodules and Cysts Form?

Nodules and cysts are seen in inflammatory acne and more severe forms of acne, such as acne conglobata. They indicate deep inflammation.

Nodules are painful balls of solid tissue over 5 mm in size. Unlike papules and pustules, which appear on the surface of the skin, nodules are deeper. In fact, they reflect the progression of inflammation into the deeper layers of the skin.

Cysts are deep, painful subcutaneous lesions. Unlike nodules, cysts are filled with a semi-solid liquid (composed of sebum, cells and dead skin). They result from the clustering of several nodules under the skin.

Nodules and cysts are the result of a deep inflammatory reaction. Cutibacterium acnes, present in the pustules, continues to proliferate, amplifying the inflammatory reaction.


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