What is the difference between PIH and PIE?

Post-inflammatory hyperpigmentation (PIH) refers to the flat brown or dark marks left after a blemish or skin inflammation. It is caused by an overproduction of melanin in response to the injury. Post-inflammatory erythema (PIE) refers to the flat pink or red marks left after a blemish, caused by dilated or damaged blood vessels near the skin surface rather than by melanin. PIH is more visible in deeper skin tones; PIE appears as pink/red discolouration and is more visible in lighter skin tones. They look similar but have different causes, and the skincare approach differs for each.

Does SPF help with post-acne marks?

Yes — especially for PIH. UV exposure stimulates melanin production and makes brown post-acne marks darker and longer-lasting. Daily broad-spectrum SPF is one of the most important steps in fading PIH, because without it, UV exposure continuously reinforces the pigmentation. For PIE (red marks), SPF is still important for general skin health but is less directly linked to the vascular mechanism.

Can you fade post-acne marks at home?

With consistent use of appropriate ingredients and daily SPF, mild to moderate PIH can fade noticeably over weeks to months. PIE typically fades more slowly and is less responsive to topical brightening ingredients — it often requires more time, and barrier-supportive ingredients (centella, ceramides) and possibly professional treatments to address the vascular component. Neither will disappear overnight — patience and consistency are essential.

Does picking blemishes make marks worse?

Yes — picking, squeezing or scratching blemishes significantly increases the risk of PIH, PIE and even scarring. The additional trauma to the skin triggers a stronger inflammatory response, which produces more melanin (PIH) or more blood vessel damage (PIE) than would occur if the blemish were left to heal naturally. This is one of the most impactful habits for managing post-acne marks — avoiding picking reduces both severity and duration of marks.

How long does it take for acne marks to fade?

It depends on the type and depth of the mark, skin tone, consistency of routine and sun protection. Mild PIH in lighter skin tones may fade within 4–8 weeks of a consistent brightening routine with daily SPF. Deeper PIH, particularly in deeper skin tones, can take 6–12+ months. PIE (red marks) often takes longer than PIH and responds less clearly to brightening ingredients. For significant or persistent marks, a dermatologist consultation is worthwhile.

Skin Concern Guide

Acne Marks — PIH & PIE

After a blemish heals, it often leaves a mark behind — either a brown or dark discolouration, or a pink or red mark. These two types of post-acne marks have different causes and respond differently to skincare, which is why understanding the distinction matters for choosing the right approach.

PIH (post-inflammatory hyperpigmentation) and PIE (post-inflammatory erythema) are the two key terms. This guide explains each in detail and outlines the Korean skincare approach to both.

General Information Only. This page provides educational skincare information and is not medical advice. If you have persistent acne, eczema, rosacea, allergies, skin irritation, pigmentation changes or any medical skin condition, please consult a qualified dermatologist or healthcare professional before changing your skincare routine. Individual results vary. Always patch test new products.

PIH vs PIE — explained

PIH — Post-Inflammatory Hyperpigmentation

Appearance: Flat brown, tan or dark marks on the skin surface
Cause: Overproduction of melanin in response to inflammation or skin injury
More visible in: Deeper skin tones (though affects all skin tones)
Worsened by: UV exposure (makes marks darker and longer-lasting)
Approach: Brightening ingredients + daily SPF

PIE — Post-Inflammatory Erythema

Appearance: Flat pink, red or purple marks on the skin
Cause: Dilated or damaged blood vessels near the skin surface after inflammation
More visible in: Lighter skin tones
Worsened by: Skin irritation, heat, pressure
Approach: Barrier repair, centella, time — and possibly professional treatment

How to tell them apart

The simplest test is to gently press a fingertip on the mark. If it turns white/paler under pressure (blanches) then returns to pink/red when you release, it is likely PIE — this is because blood vessels empty and refill. If the mark remains the same colour when pressed, it is more likely PIH (pigmentation does not blanch).

Some marks are a combination of both — a blemish can cause both excess melanin production and blood vessel changes simultaneously.

For PIH — brightening approach

Niacinamide (5%)

May reduce melanin transfer to skin cells — a key mechanism for reducing PIH.

Vitamin C

Antioxidant with brightening properties — use in morning under SPF.

Azelaic acid

Well-regarded for PIH — gentle enough for sensitive skin.

Alpha-arbutin

A stable brightening ingredient that may inhibit melanin-producing enzyme activity.

Daily SPF (essential)

UV exposure makes PIH darker and prolongs it significantly — SPF is non-negotiable.

Gentle AHA (1-2x/week)

Lactic acid helps support cell turnover and surface brightening.

For PIE — barrier and vascular approach

Centella asiatica

Calming and supportive of skin healing — widely used in K-beauty for post-blemish care.

Ceramides

Barrier repair — a healthy barrier supports better healing and reduces ongoing reactivity.

Niacinamide

Also useful for PIE in terms of general skin health and reducing redness over time.

Time and patience

PIE fades more slowly than PIH — most red marks take at least 3-6+ months even with consistent care.

The most important habit: stop picking

Picking, squeezing or scratching blemishes is the single most impactful behaviour for worsening both PIH and PIE — and for increasing the risk of true scarring (texture changes, indented scars), which is much harder to address than flat marks. If you struggle with picking, this is a habit worth addressing alongside your skincare routine. Leaving blemishes to heal naturally produces significantly less post-inflammatory pigmentation in most cases.

Timeline expectations

Mild, recent PIH may show visible improvement in 4–8 weeks of consistent treatment with brightening ingredients and daily SPF. Older or deeper PIH, particularly in deeper skin tones, takes significantly longer — often 3–12 months. PIE is generally slower to fade and less responsive to topical brightening ingredients. Both require consistency and patience — there are no overnight solutions.