What Is Post-inflammatory Erythema (PIE)?

Post-inflammatory erythema, commonly shortened to PIE, is a term that was first introduced in dermatology literature in 2013 by Bae-Harboe et al. to describe erythema (redness of the skin or mucous membranes, caused by hyperemia (increased blood flow) in superficial capillaries), often seen after the resolution of inflammatory acne or other inflammatory skin conditions.

After a breakout or a more serious case of acne many people are left with hyperpigmentation (dark or red spots) that can be categorised as either PIE or PIH (post-inflammatory hyperpigmentation).

So, how do you know which one you have?


The cause is the same, so to differentiate them you have to look at the aftermath of a breakout.

There is a really simple way to tell which one you’re dealing with – if the spot is brown or dark, it’s PIH. If it’s pink, red or purplish, it’s PIE.

Well, this may seem simple in theory BUT when it comes down to it the variety of skin tones may make it difficult to definitively say whether your post-inflammatory mark is red or brown. In that case all you need to do is press on your skin where the spot is, and if it momentarily disappears, it’s most likely PIE. If the mark doesn’t disappear, it’s probably PIH.

How do you calm redness from post-inflammatory erythema?

PIE does not involve melanin at all, so it’s treated differently to PIH (which involves melanin production inhibition and why its more common in darker skin tones).

As PIE is the result of damaged capillaries under the skin, intense treatment includes using Intense Pulsed Light and Pulsed Dye Lasers to reach below the surface of the skin to break down damaged blood vessels.

For a less intensive treatment and to fade any hyperpigmentation, skin brighteners such as vitamin C and niacinamide have been recommended by dermatologists.

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