Blackhead or open comedo: what is it?

Also called an open comedo, the blackhead is a retention lesion that represents the first stage of acne. This skin imperfection results from a biological dysfunction within the pilosebaceous follicle. It all begins with hyperseborrhoea, that is, an excessive production of sebum, combined with hyperkeratinisation. The latter refers to an abnormal build-up of dead cells on the surface of the skin. This compact mixture eventually blocks the pore and creates a plug, more precisely a comedo.

On contact with air, the lipids contained in this plug oxidise, turning the end of the comedo into a small, black, hard bead at the surface of the skin.

This type of blackhead is observed to appear mainly in areas rich in sebaceous glands. The face is the most exposed area, with a high concentration in the T‑zone, often leading to the formation of blackheads on the nose or comedones on the nose. However, other, more unexpected areas may also be affected: it is not uncommon to see a blackhead in the ear or a black spot on the ear, where the skin is also thin and prone to secretions. Similarly, the perioral areas are susceptible to these blemishes. One may therefore notice the presence of blackheads around the mouth, blackheads around the lips, or precisely along the lip border.

If left untreated, these comedones can progress in two ways. They may rupture and release their contents under the pressure of a comedone extractor or the fingers, with a risk of scarring. More problematically, the blackhead can become inflamed under the action of bacteria such as Cutibacterium acnes, thereby progressing to an inflammatory stage.

Although the formation of a blackhead is a natural physiological process, several internal and external factors can accelerate pore blockage and increase the number of blackheads. The main ones are as follows:

• Hormonal fluctuations : Androgen hormones play a predominant role in activating the sebaceous glands. During puberty, pregnancy, menstrual cycles, or after stopping an oral contraceptive pill, sebum production tends to increase. This hormone-induced hyperseborrhoea often explains why the open comedone appears in a cyclical manner.

• The nature of the skin : Combination to oily skin types are intrinsically more prone to acne of the retention type. By nature, these skin types have more active sebaceous glands and more dilated pores, which facilitates the clustering of corneocytes. This explains the recurrence of comedones on the nose, or blackheads on the nose, where the density of glands is highest.

• The use of unsuitable cosmetics : The application of so‑called "comedogenic" products can create an occlusive film that prevents the natural flow of sebum and promotes the formation of blackheads.

• Environmental factors : Pollution and exposure to UV radiation also contribute to the oxidation of squalene, a component of sebum, making it more viscous and darker, which promotes the formation of blackheads.

Even if it is tempting, it is better to avoid removing a blackhead by extracting it manually.

Squeezing a blackhead with your fingers, whether it is a blackhead on the nose or a blackhead on the ear, risks damaging the surrounding tissues, spreading bacteria and turning a simple retention lesion into an inflammatory spot. Although the occasional, sterile use of a comedone extractor can be considered, the most effective approach remains the use of keratolytic active ingredients. Salicylic acid is the reference active ingredient here: by penetrating into the pore, it dissolves the plug of sebum and dead cells, making it easier to clear the open comedone without irritating the skin.

Cleansing is the other fundamental pillar for preventing and reducing blackheads. A double cleanse in the evening, starting with a cleansing oil, makes it possible to dissolve lipid-based substances by affinity, such as sebum, sunscreens and make-up, before continuing with an aqueous cleanser. By clearing the opening of the pilosebaceous duct on a daily basis, the oxidation of lipids and the formation of new blackheads are thereby limited.

Finally, a complete skincare routine should be followed by the application of a moisturising cream and a sunscreen in the morning. Contrary to some common beliefs, skin prone to blackheads should not be dried out, as this may trigger a defensive overproduction of sebum, a phenomenon known as reactive hyperseborrhoea. In addition, using a purifying mask once or twice a week, for example one based on clay, can help absorb excess oil and prevent blackheads.

In the case of numerous, recurrent, or distressing blackheads, it is also possible to turn to aesthetic medicine solutions, such as laser treatment or chemical peels.

• MILLS O. & al. Microbiology of comedones in acne vulgaris. Journal of Investigative Dermatology (1973).

• WU I-T. & al. Clinical evaluation of salicylic acid scrub, toner and mask in reducing blackheads. Journal of the American Academy of Dermatology (2004).

• JIN C. & al. Effectiveness of the optimal pulse technology in a novel technique for treating nasal blackheads in Asians: A clinical study. Journal of Cosmetic Dermatology (2025).