Closed comedones or microcysts
These are the same colour as the skin. With these lesions, the pilo-sebaceous follicle’s hair duct is blocked. Sebum can no longer flow normally and a small bump forms beneath the skin that appears to have a white spot at the centre.


Open comedones or “blackheads”
They can measure 1 to 3 mm in diameter and their black colour is caused by the oxidation of lipids when exposed to air. This type of lesion can progress to a papule or pustule, i.e. an inflammatory red spot. In order for a blackhead to become an inflamed red spot, all that’s needed is for the Cutibacterium acnes acne bacterium to get involved... Hence the importance of treating blackheads as soon as they develop, before inflammation causes the situation to worsen.


Open comedones can turn into inflamed lesions when they are colonised by Cutibacterium acnes, the specific bacterium involved in acne. These comedonal lesions then become inflammatory lesions or red spots, referred to as papules by dermatologists. With diameters of 1 to 4 millimetres, they often have a red ring around them and are often painful. Papules can also appear spontaneously without there being a pre-existing blackhead.


When this inflammation worsens, pustules form on top of the papules, which is a condition that professionals refer to as papulo-pustular acne. The pustules are filled with an infected white or yellow fluid that may be evacuated or migrate more deeply into the skin. They then form either nodules or cysts. Cystic acne is the most severe form of acne and the hardest to treat.

Cystic acne

This is the final stage in the progression of acne. Either cysts naturally appear in the context of persistent acne and severe inflammatory lesions, or they form when pimples have been picked at and squeezed multiple times.

With cystic acne, the comedo is contained within a fibrous shell that prevents sebum from flowing outward as it usually would. The cyst is hard and deep and may persist for several months or even years. It may seem to disappear and then reappear depending on the state of inflammation or the patient’s menstrual cycle.

Hard to remove due to their depth, these cysts are also the lesions that can leave the most scars. Attempts to manually pop them are thus not only ineffective but can leave marks in the long term.

  • Benoit Cadars, scientific expert at Bioderma
    Benoit Cadars , Scientific Attaché, BIODERMA.


    Acne-prone skin can be subject to various types of blemishes, each of which requires a specific solution. In BIODERMA’s Sébium range, Sébium Sensitive is mainly intended for three types of cases where the inflammatory factor is always predominant:

    Traditional acne

    For patients with red and painful inflamed pimples but not for comedonal acne, since Sébium Sensitive has no keratolytic action. If you have blackheads, choose Sébium Global.

    Adult acne

    In adulthood, there are fewer pimples but they are often highly inflamed:
    adult acne is characterised by papules, pustules and nodules. The active ingredients in Sébium Sensitive contribute to rebalancing sebum composition to bring it closer to that of healthy skin.

    Acne-prone skin undergoing keratolytic treatment

    Sébium Sensitive is recommended for patients undergoing keratolytic treatment (for topical application) since it offsets their drying effect with no risk of causing new blemishes, unlike certain traditional moisturising products that have not been tested for their comedogenic potential. Sébium Hydra is more suitable for use in combination with highly drying treatments, especially isotretinoin.

    Benoit Cadars , Scientific Attaché, BIODERMA.