How can a blackhead develop?

Blackheads (open comedones) are retentional lesions of the epidermis. They most often appear on combination to oily skin, which is characterized by high sebum production and more visible pores, but all skin types can be affected. They are found mainly in the T-zone, which includes the forehead, nose, and chin, where the concentration of sebaceous glands is particularly high. This density promotes increased sebum secretion, which can contribute to clogging the pores.

This phenomenon is often accompanied by a disruption of the skin’s natural desquamation process, the mechanism by which it sheds dead cells. Their accumulation, combined with excess sebum, forms a plug within the pilosebaceous follicle. When exposed to air, this mixture gradually oxidizes and turns black. Several factors can promote this hyperseborrhea and the formation of comedones, including hormonal fluctuations, certain dietary factors, pollution , and exposure to UV radiation.

Did you know? A blackhead measures between 1 and 3 mm in diameter, and its color is due to the oxidation of sebum when it comes into contact with air.

Depending on the circumstances, a blackhead can develop in several different ways.

First possible outcome: The blackhead resolves.

The first possible development of a blackhead, and the most favorable one, is its elimination from the pore, whether it is spontaneous or mechanically assisted. Over time, the plug made up of oxidized sebum and dead cells can gradually migrate toward the surface of the skin under the effect of epidermal renewal. This slow process depends in particular on the rate of desquamation and the balance of sebum production. In some cases, the comedone can therefore be expelled naturally, but this process may take several weeks or even several months.

Mechanical extraction, particularly using a comedone extractor, helps speed up this process by applying controlled pressure around the pore, which leads to the rupture of the plug and the expulsion of the follicular contents in the form of a filament. However, this procedure is not without consequences: excessive or poorly directed pressure can damage the wall of the pilosebaceous follicle, promote an inflammatory reaction, or result in micro-lesions.

For this reason, it is recommended not to manipulate blackheads yourself, but to entrust their extraction to a dermatologist.

Second possible development: The blackhead becomes inflamed.

The blackhead can progress into an inflammatory lesion, characterized by the appearance of a red bump that is sensitive to touch. This transformation is mainly driven by the proliferation of the bacterium Cutibacterium acnes, which is naturally present within the skin microbiota. In a sebum-rich environment, such as that of a blocked follicle, this bacterium finds favorable conditions for its growth. It hydrolyzes the triglycerides in sebum into free fatty acids, which are irritating compounds capable of damaging the follicular wall and triggering a local inflammatory response.

This inflammation is accompanied by an infiltration of immune cells and the release of pro-inflammatory mediators, which result in redness and swelling. When the inflammation remains superficial, it appears in the form of papules and pustules. In contrast, if it extends deeper, it can lead to the formation of nodules that are larger and more painful, and may even develop into cystic lesions. The intensity of this progression depends in particular on the bacterial load, the amount of sebum present, and the individual reactivity of the immune system.

Third possible development: The blackhead becomes infected.

Beyond the inflammation related toCutibacterium acnes, a blackhead can also progress to a true infection, such as folliculitis, which is often promoted by repeated manipulation. Touching, squeezing, or trying to extract a comedo with the fingers exposes the follicle to exogenous microorganisms, especially bacteria present on the hands or under the nails. This contamination can lead to a worsening of the initial inflammatory reaction and promote the development of more extensive lesions.

Furthermore, mechanical manipulation can weaken, or even rupture, the wall of the pilosebaceous follicle. This rupture releases the contents of the comedone—sebum, keratin, and bacteria—into the dermis, where they are recognized by the body as foreign material. This triggers a more intense inflammatory reaction, sometimes associated with a secondary infection, and increases the risk of residual marks.

This is why it is important not to touch your blackheads, especially not with unwashed hands.

A study to explore further the progression of comedones (blackheads).

Although scientific studies on how blackheads evolve are scarce, there is a study conducted in 1974 by DURR and his team in an adolescent that made it possible to follow the progression of 30 open comedones. Thanks to repeated photographs, the researchers observed that blackheads could persist in a non-inflammatory state for several weeks, or even several months — some remained stable for at least 98 days — while gradually increasing in diameter. Subsequently, these lesions, even when not manipulated, frequently progressed to inflammatory forms, characterized by the appearance of erythema and edema, and then to pustular lesions.

The results also show that the average time for an inflammatory lesion to progress to resolution is about 13 days.

In addition, a trend was observed: the longer a comedo persists in a non‑inflammatory state, the more the subsequent inflammatory and pustular phase tends to be prolonged. Although these data are based on observation of a single patient, which limits their generalizability, they suggest that open comedones are dynamic lesions likely to progress spontaneously toward inflammatory forms, and that their early removal, when performed in a non‑traumatic manner, could reduce this risk of progression.

• DURR N. P. & al. The natural evolution of comedones into inflammatory papules and pustules. Journal of Investigative Dermatology (1974).

• DOSHI N. B. & al. New researches on acne vulgaris. Research Journal of Pharmacology and Pharmacodynamics (2011).

• LIU Y. & al. Complementary therapies for acne vulgaris. The Cochrane Database of Systemic Reviews (2015).