What is post-inflammatory erythema?

Post-inflammatory erythema manifests as pink to red spots that appear on the skin following inflammation, such as that caused by acne or severe irritation. These marks are not true scars per se, 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 skin phototypes with darker tones and manifests as brown spots. Post-inflammatory erythema is linked to blood vessel dilation, while the post-inflammatory hyperpigmentation results from an overproduction of melanin.

Thus, as its name suggests, post-inflammatory erythema is the result of skin inflammation.

In the case of inflammatory acne, hyperseborrhea 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 results in intensified blood flow to the infected area, aiming to supply immune cells with the nutrients and oxygen needed to combat pathogens. However, this vasodilation also causes local redness, which leads to post-acne erythematous marks.

Post-inflammatory erythema gradually resolves over several months, often between 3 and 12 months, but 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 resolves: sun exposure, which can delay clearance by promoting inflammation and vascular dilation; skin sensitivity, often more pronounced in lighter phototypes; and topical care, since certain irritating products may extend the redness.

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

Cosmetic treatments to reduce post-inflammatory erythema.

• Adequate skin hydration...

  Hydration is a key factor in wound healing. To accelerate the fading of erythematous marks, we recommend applying a moisturizing treatment daily, containing, for example, panthenol or Centella asiatica. Also known as provitamin B5, the former is recognized for its ability to absorb moisture from the air to boost the water content of the stratum corneum. The Centella asiatica is, in turn, an Asian plant with a similar mechanism of action and provides additional anti-inflammatory and soothing properties.

• ... complemented by active ingredients targeting inflammation.

  The clearance of post-inflammatory erythema can also be accelerated by incorporating anti-inflammatory ingredients into the skincare routine. Among the best-known are azelaic acid, the niacinamide, the bisabolol, the turmeric, the ferulic acid and the licorice extract. Acting at various stages of inflammation, these molecules help reduce redness and allow the skin to regain its uniformity.

Reducing erythematous spots: an in-depth look at dermatological techniques.

• The laser.

  The use of lasers, such as the Nd:YAG laser, has demonstrated its effectiveness in various studies. To be performed only 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 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 obtaining visible results on a post-inflammatory erythema.

• The pulsed light.

  Using a process similar to that of lasers, intense pulsed light differs by its broader range of emitted wavelengths (500–1200 nm). Its ability to significantly reduce erythematous marks has been demonstrated in various studies. In a recent study involving 33 patients with post-inflammatory erythema, 3 to 6 sessions of intense pulsed light improved skin color and texture in the majority of patients and to achieve the near-complete disappearance of the marks in 27 patients, as illustrated by the photos below. However, temporary pigmentary disorders (hyper- or hypopigmentation) were nonetheless observed in 9 patients.

• The radiofrequency.

  Primarily known for its effects on signs of aging, fractional radiofrequency can also be used to reduce post-inflammatory erythema. By delivering an electrical current, it creates coagulation zones at various depths of the skin to stimulate fibroblast activity, the cells responsible for synthesizing collagen and elastin. The goal of radiofrequency is to promote tissue regeneration. A recent study demonstrated a significant reduction of post-inflammatory erythema in 25 patients, with no side effects after two radiofrequency sessions.

Although erythematous marks typically fade over time, preventing them remains the best strategy. To achieve this, it is essential to manage acne at its onset. Early dermatological monitoring limits the duration and intensity of inflammatory episodes, the main drivers of persistent capillary dilation. The shorter the inflammation, the lower the risk of post-inflammatory erythema, as well as scarring.

At the same time, maintaining a skin barrier intact is essential. Even oily skin requires hydration: a proper hydrolipidic balance reduces transepidermal water loss, protects the skin from external aggressors, and helps rebalance sebum production by preventing reactive hyperseborrhea. Proper hydration also strengthens the skin barrier, promoting wound healing.

Another reflex: avoid touching your pimples. Squeezing or scratching a lesion intensifies capillary rupture and prolongs the local inflammatory reaction. This therefore increases the likelihood of developing red marks or scars. Even if it may be tempting, touching your pimples won’t make them go away faster; in fact, it will have the opposite effect.

Finally, it is important to know that sun exposure intensifies post‐inflammatory erythema and prolongs the healing process. UV radiation increases vasodilation and stimulates free‐radical production, which sustains post‐inflammatory redness. Therefore, be sure to protect yourself daily from UV rays by applying a broad‐spectrum SPF sunscreen. Additionally, if you must go outdoors during peak sun hours—between 11 a.m. and 4 p.m.—we recommend wearing sunglasses and a wide‐brimmed hat or a cap.

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• 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).