What is post-inflammatory erythema?

It is quite common to have pigmented spots after acne. To be differentiated from thepost-inflammatory hyperpigmentation, which is more characteristic of darker phototypes, post-inflammatory erythema presents itself in the form of pink to red spots where the blemishes were previously located. Although they can have a real impact on the uniformity of the complexion and self-confidence, these marks are not considered scars as they gradually fade over time. However, their complete disappearance can be quite lengthy and takes several months.

As its name suggests, post-inflammatory erythema results from a skin inflammation. In the case of inflammatory acne, hyperseborrhea is accompanied by the proliferation of the bacterium Cutibacterium acnes. This microorganism thrives in oily environments by feeding on sebum. Cutibacterium acnes plays a major role in inflammation: indeed, it digests the triglycerides present in the sebum and releases pro-inflammatory fatty acids, thereby causing inflammation of the sebaceous glands.

Inflammation then triggers a local immune response in the skin, during which certain immune cells such as neutrophils and macrophages are recruited. Concurrently, chemical mediators of inflammation like interleukins and prostaglandins are released into the skin. They amplify skin inflammation and stimulate vasodilation. The increase in blood vessel diameter results in an intensification of blood flow to the infected area, with the aim of providing immune cells with the necessary nutrients and oxygen to combat pathogens. However, this vasodilation can also lead to local redness, which is the origin of post-acne erythematous marks. This can persist even after the acne has disappeared and the tissues have healed.

Unlike an atrophic or hypertrophic scar, a post-inflammatory erythema usually eventually fades. This rather lengthy process can be accelerated through the regular application of certain cosmetic actives or via dermatological techniques.

Cosmetic treatments for reducing post-inflammatory erythema.

• Proper skin hydration...

  Hydration is a key factor in healing. To accelerate the disappearance of erythematous marks, we advise you toapply a moisturising treatment daily, containing, for example, panthenol or Centella asiatica. Also known as provitamin B5, the former is an active ingredient recognised for its ability to absorb moisture from the air to increase the water content of the stratum corneum. Centella asiatica is an Asian plant with a similar mechanism of action, which also has anti-inflammatory and soothing properties.

• ... supplemented with active ingredients targeting inflammation.

  The disappearance of post-inflammatory erythema can also be accelerated by incorporating anti-inflammatory actives into one's skincare routine. Among the most renowned are azelaic acid, niacinamide, bisabolol, turmeric, ferulic acid, and liquorice extract. Acting at different stages of inflammation, these molecules help to reduce redness and allow the skin to regain its uniformity.

Diminishing erythematous spots: a closer look at dermatological techniques.

• The laser.

  The use of lasers, such as Nd-YAG lasers, has demonstrated its effectiveness in various studies. This treatment should only be carried out by a trusted healthcare professional, and is preferably done in winter, requiring strict sun protection in the days before and after the session. The principle of the laser is based on the emission of a specific wavelength that destroys inflamed skin cells. Several sessions may be necessary before visible results are achieved.

• Pulsed light.

  Utilising a process similar to that of a laser, pulsed light differentiates itself by its broader range of emitted wavelengths (between 500 and 1200 nm). Its ability to significantly reduce erythematous marks has been demonstrated in various studies. In a recent study conducted with 33 patients suffering from post-inflammatory erythema, 3 to 6 sessions of pulsed light improved the colour and texture of the skin in the majority of patients and led to the near disappearance of marks in 27. However, temporary pigment disorders (hyper- or hypopigmentation) were encountered by 9 patients.

• Radiofrequency.

  Primarily known for its effect on signs of ageing, fractional radiofrequency can also be used to reduce post-inflammatory erythema. By emitting an electric current, it creates coagulation zones at various depths of the skin to stimulate the activity of fibroblasts, the cells that synthesise collagen and elastin. The aim of radiofrequency is to induce a tissue regeneration. A recent study showed a significant reduction in post-inflammatory erythema in 25 patients with no side effects after two sessions of radiofrequency.

While erythematous marks generally tend to fade away, preventing them through certain precautionary measures remains the best solution. For this, we advise you tovisit a dermatologist without delay to treat your acne as soon as possible, before the spots spread across your skin and leave stains, or even scars. A tailored follow-up by a healthcare professional will save you time in your fight against acne.

In parallel, it is essential to properly hydrate your skin daily, even if you have oily skin. Indeed, this action is crucial to limit insensible water loss, which affects all skin types, to protect against external aggressions, and thereby, rebalance the sebum level. Good hydration also strengthens the skin barrier which promotes healing. Moreover, to avoid exacerbating inflammation and spreading the infection, avoid handling your spots. This will not make them disappear faster, on the contrary.

Finally, it is important to know that sun exposure intensifies post-inflammatory erythema and prolongs the healing time. Therefore, make sure to protect yourself daily from UV rays by applying a broad-spectrum SPF sunscreen. If you need to go out during the hours of the day when the sun is at its highest, which is between 11am and 4pm, we advise you to equip yourself with sunglasses and a wide-brimmed hat or a cap.

• BAE-HARBOE Y. S. & GRABER E. M. Simple as PIE (Postinflammatory Erythema). The Journal of Clinical and Aesthetic Dermatology (2013).

• SUH D. H. & co. Fractional Microneedling Radiofrequency Treatment for Acne. Acta Dermato-Venereologica (2015).

• ABAD-CASINTAHAN F. & others. Frequency and characteristics of acne-related post-inflammatory hyperpigmentation. The Journal of Dermatology (2016).

• AISWARYA V. & al. Intense Pulsed Light Therapy for Acne-induced Post-inflammatory Redness. Indian Dermatology Online Journal (2018).

• ETESAMI I. & al. Treatment of post-acne erythema: A systematic review of the literature. Journal of Cosmetic Dermatology (2022).

• AFLATOONIAN M. & al. Treatment protocols and efficacy of light and laser treatments in post-acne erythema. Journal of Cosmetic Dermatology (2022).