How can we reduce or even eliminate the marks left by acne?

Even after the blemish has disappeared, acne can leave marks on the skin. Among these traces, you will find:

• Post-inflammatory hyperpigmentation marks , which are a type of hyperpigmentation, present themselves as persistent flat brown or black spots, depending on skin colour, that are generated following an increased production of melanin in response to an inflammatory reaction. Indeed, the appearance of these hypercoloured areas relies on the production of inflammatory cytokines, which have pro-pigmenting properties, by the surrounding cells. They activate the melanocytes (cells that produce melanin), leading to a significant release of melanosomes (pigment granules) and thus an excess of melanin. Although this phenomenon can affect all skin types, it is generally more common in individuals with mixed to dark skin (phototypes IV to VI).

• Post-inflammatory erythema (PIE) are persistent flat pink-reddish spots that appear following inflammatory acne. When the skin undergoes a bacterial infection, the blood circulation in the area of the blemish increases. Thus, these marks are caused by the dilation of the blood capillaries. These red marks are more visible on fair skin.

Unlike acne scars, these marks are temporary and usually disappear spontaneously without leaving scars after several months (between 3 to 24 months). Sometimes, it can take several years. However, the speed of their disappearance depends on your exposure to the sun, which can prolong the healing time, but also on the difference in skin tone between the colour of the skin and the shade of the mark.

Individuals suffering from EPI inevitably experience a reduction in the lipid barrier function of the epidermis. However, the most fundamental aspect is to maintain hydrated skin, as it requires water to heal effectively. Therefore, the treatments used should target inflammation, as well as the repair and maintenance of the skin barrier. The following agents should be prioritised:

• Azelaic Acid: In addition to its antioxidant activity, azelaic acid also possesses anti-inflammatory properties. Studies have shown that azelaic acid inhibits the secretion of pro-inflammatory cytokines, such as interleukins IL-1β and IL-6, and the transcription factor TNF-α. Furthermore, another study demonstrated that azelaic acid promotes the regulation of kallikrein-5 (a serine protease) in epidermal keratinocytes, which in turn lower cathelicidins (anti-microbial peptides), reducing inflammatory processes.

• Centella asiatica : This herbaceous plant, native to Asia, is used in cosmetics for its healing and restorative properties, attributed to the presence of madecassoside and asiaticoside. It is also valued for its hydrating action, due to the presence of sugars that have a strong affinity with water, thereby increasing the skin's moisture levels. Finally, the Centella asiatica also has anti-inflammatory activity, thus reducing inflammation.

• Ceramides: These are lipids naturally present in the skin, making up 50% of the skin barrier. The ceramides in skincare products help to regenerate the skin's ceramides, thereby restoring the lipid layer of the epidermis. They thus aid in keeping the skin hydrated and protected against external aggressions, thereby limiting irritations. Indeed, they maintain the cohesion of the various elements of the skin and form a protective layer.

• Niacinamide: This vitamin boosts the synthesis of ceramides, free fatty acids, and cholesterol, which are contained within the intercellular spaces of the stratum corneum, thereby promoting a functional skin barrier and thus maintaining a good hydration level. It also possesses anti-inflammatory properties.

• Panthenol: Also known as provitamin B5, this cosmetic ingredient has the ability to absorb and retain moisture from the air to increase the water content of the stratum corneum, as well as to create a film on the skin's surface to reduce transepidermal water loss. Clinical studies have also reported its healing potential by stimulating cell growth, which would consequently reduce healing time.

To address acne scars, there are other options available. These range from topical medicinal solutions to laser treatments and chemical peels:

• Pulsed Light: This non-invasive and non-ablative treatment utilises high-intensity light pulses. To eliminate brown spots, pulsed light targets the melanin on the skin's surface to fade the discolouration.

• Chemical Peeling: The principle of peeling is somewhat similar to that of exfoliation. It involves applying a chemical substance (glycolic acid, salicylic acid, trichloroacetic acid, etc...) in various concentrations to the skin to trigger a controlled desquamation of the epidermis, and with it the melanocytes and the marks left by spots. Indeed, blisters form and eventually peel off, leaving behind smooth skin without hyperpigmentation. This procedure should be carried out by a dermatologist, preferably in autumn or winter.

• Low-energy Pigment Laser Therapy: The aim is to destroy hyperpigmented skin cells using high-energy light so that new, flawless skin can emerge. However, this treatment can cause minor damage (burning sensation, irritation...) and lead to the onset of PIH (Post-Inflammatory Hyperpigmentation).

• Kligman's Trio: Dr. Kligman developed a formula based on the unique synergy of three components: hydroquinone (a tyrosinase inhibitor), hydrocortisone (anti-inflammatory action), and retinoic acid (accelerates cell renewal). Together, they have demonstrated a depigmenting power on the various stages of the melanin cycle. The effects of depigmentation appear after 3 to 5 weeks of treatment. However, this solution can cause irritations and sensitivity. Moreover, it does not rule out a recurrence of brown spots.