What is post-inflammatory erythema?

Post-inflammatory erythema manifests as pink to red spots that appear on the skin following an inflammatory episode, such as that caused by acne or intense irritation. These marks are not scars in the strict sense, as they do not alter the deeper structure of the skin and tend to fade gradually over time, although their resolution can be slow. Post-inflammatory erythema must be distinguished from post-inflammatory hyperpigmentation, which predominantly affects darker phototypes darker ones and presents as brown spots. Post-inflammatory erythema is linked to dilation of blood vessels, whereas the post-inflammatory hyperpigmentation results from an overproduction of melanin.

Thus, as its name suggests, post-inflammatory erythema results from inflammation of the skin.

In the case of inflammatory acne, hyperseborrhoea promotes the proliferation of the bacterium Cutibacterium acnes, which feeds on sebum and releases pro-inflammatory fatty acids. This activity triggers a local immune response: neutrophils and macrophages, immune cells, are recruited, and chemical mediators of inflammation, notably interleukins and prostaglandins, are released. These molecules amplify inflammation and stimulate vasodilation. This increase in blood vessel diameter leads to an intensified blood flow to the infected area, aiming to supply immune cells with the nutrients and oxygen needed to combat the pathogens. However, this vasodilation also causes local redness, which underlies the post-acne erythematous marks.

Post-inflammatory erythema gradually fades over several months, often between 3 and 12 months, although some marks may persist for up to 24 months.

The persistence of these erythematous marks varies according to the intensity of the initial inflammation, the depth of the lesion and the phototype of the skin. Several factors influence the rate at which post-inflammatory erythema disappears: sun exposure, which can slow resorption by promoting inflammation and vasodilatation; skin sensitivity, often more pronounced in fair complexions; and the care products applied, as certain irritating formulations may prolong redness.

Unlike an atrophic or hypertrophic scar, a post-inflammatory erythema will ultimately fade. This relatively protracted process can be accelerated by the regular application of certain active cosmetic ingredients or via dermatological techniques.

Cosmetic treatments to reduce post-inflammatory erythema.

• Proper skin hydration...

  Hydration is a key factor in healing. To accelerate the disappearance of erythematous marks, we recommend applying 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 water content in the stratum corneum. The Centella asiatica is an Asian plant with a similar mechanism of action, complemented by anti-inflammatory and soothing properties.

• … supplemented with active ingredients targeting inflammation.

  The resolution of post-inflammatory erythema can also be accelerated by adding anti-inflammatory actives into a skincare routine. Among the best-known are azelaic acid, the niacinamide, the bisabolol, the turmeric, the ferulic acid and the liquorice extract. Acting at different stages of inflammation, these molecules help to reduce redness and allow the skin to regain its uniform appearance.

Reducing erythematous patches: a closer look at dermatological techniques.

• The laser.

  Use of lasers, such as the Nd-YAG laser, has demonstrated its efficacy in various studies. Should only be performed by a healthcare professional you trust, this treatment is preferably carried out in winter and must be accompanied by strict sun protection on the days preceding and following the session. The principle of the laser relies on the emission of a specific wavelength allowing the destruction of inflamed skin cells. Several sessions may be required before visible results are achieved on a post-inflammatory erythema.

• The pulsed light.

  Using a process similar to that of the laser, intense pulsed light is distinguished by its broader range of emitted wavelengths (between 500 and 1200 nm). Its ability to significantly attenuate erythematous marks has been demonstrated in various studies. In a recent study involving 33 patients with post-inflammatory erythema, 3 to 6 sessions of pulsed light treatment improved skin colour and texture in the majority of patients and resulted in the near-complete disappearance of the marks in 27 of them, as illustrated in the photographs below. Temporary pigmentary disturbances (hyper- or hypopigmentation) were nevertheless observed in 9 patients.

• The radiofrequency.

  Best known for its effects on signs of ageing, fractionated radiofrequency can also be used to reduce post-inflammatory erythema. By emitting an electric current, it creates some coagulation zones at different depths of the skin in order to stimulate fibroblast activity, the cells responsible for synthesising collagen and elastin. The aim of radiofrequency is to induce tissue regeneration. A recently published study demonstrated a significant reduction in post-inflammatory erythema among 25 patients with no side effects after two radiofrequency sessions.

Although erythematous lesions generally fade over time, preventing them remains the most effective strategy. To this end, it is essential to manage acne from its first appearance. Early dermatological follow-up limits the duration and intensity of inflammatory episodes, the primary drivers of persistent capillary dilation. The shorter the inflammatory episode, the lower the risk of post-inflammatory erythema, as well as of scarring.

Meanwhile, maintaining an skin barrier intact is essential. Even oily skin needs hydration: a good hydrolipidic balance reduces insensible water loss, shields the skin from external aggressors and helps rebalance sebum production by preventing reactive hyperseborrhoea. Proper hydration also reinforces the skin barrier, promoting healing.

Another reflex: avoid handling your spots. Squeezing or picking at a lesion increases capillary rupture and prolongs the local inflammatory response. This action therefore raises the likelihood of developing red marks or scars. Although it may be tempting, touching your spots will not make them go away any faster; on the contrary.

Finally, it is helpful to know that sun exposure worsens post-inflammatory erythema and extends the healing time. Indeed, UV rays increase vasodilation and stimulate free radical production, thereby maintaining post-inflammatory redness. Ensure you protect yourself daily from UV radiation by applying a broad-spectrum SPF sunscreen. Moreover, if you need to go out when the sun is at its highest, between 11 am and 4 pm, we recommend wearing sunglasses and a wide-brimmed hat or cap.

• YOUN S. W. & al. Acne erythema improvement by long‐pulsed 595‐nm pulsed‐dye laser treatment: A pilot study. Journal of Dermatological Treatment (2008).

• BAE-HARBOE Y. S. & al. Easy as PIE (Postinflammatory Erythema). The Journal of Clinical and Aesthetic Dermatology (2013).

• SUH D. H. & al. Fractional microneedling radiofrequency treatment for acne. Acta Dermato-Venereologica (2015).

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

• HAMZAVI I. & al. Postinflammatory hyperpigmentation: A comprehensive overview: Epidemiology, pathogenesis, clinical presentation, and noninvasive assessment technique. Journal of the American Academy of Dermatology (2017).

• AISWARYA V. & al. Intense pulsed light therapy for acne-induced post-inflammatory erythema. Indian Dermatology Online Journal (2018).

• HAYASHIBE K. & al. Effect of a cosmetic use with 2% isostearyl-L-ascorbic acid gel for postinflammatory hyperpigmentation and postinflammatory erythema in acne vulgaris. Journal of Cosmetics Dermatological Sciences and Applications (2020).

• ETESAMI I. & al. Post-acne erythema treatment: 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).