Post-Inflammatory Erythema (PIE): Why Acne Leaves Red Marks

Post-Inflammatory Erythema (PIE): Why Acne Leaves Red Marks

If your acne has healed but you're left with flat pink, red or purple marks, you're most likely experiencing Post-Inflammatory Erythema (PIE).

These marks are extremely common after inflammatory acne, particularly in lighter skin tones. Although they can be frustrating and sometimes persist for months, they are not true acne scars. They are a temporary result of inflammation affecting the tiny blood vessels within the skin.

Understanding why PIE develops and how it differs from pigmentation can help you feel more confident about what you're seeing and what to expect during the healing process.

What is Post-Inflammatory Erythema (PIE)?

Post-Inflammatory Erythema is a flat area of redness that remains after an inflamed spot has healed.

Unlike Post-Inflammatory Hyperpigmentation (PIH), which is caused by excess pigment, PIE is caused by tiny blood vessels near the surface of the skin that remain dilated or more visible following inflammation.

The marks may appear:

  • Pink.
  • Red.
  • Purple.

Importantly, the skin remains smooth.

There is no change in skin texture, making PIE very different from true acne scarring.

Who is most likely to develop PIE?

PIE is generally most noticeable in:

  • Fair skin.
  • Light skin tones.
  • People who flush easily.

Because redness is easier to see in lighter complexions, PIE tends to be much more visible than it is in darker skin tones.

It most commonly develops after inflamed acne lesions have healed, leaving behind a persistent red shadow where the spot once was.

How long does PIE last?

PIE usually fades gradually over weeks to months.

The exact timeframe varies depending on:

  • The severity of the original inflammation.
  • Your skin type.
  • Whether further irritation occurs.
  • Whether new acne continues to develop.

Repeated inflammation in the same area, particularly from picking or squeezing spots, can prolong recovery.

What helps PIE improve?

Be gentle with your skin

Avoid anything that creates additional inflammation.

This includes:

  • Picking spots.
  • Harsh scrubbing.
  • Aggressive exfoliation.
  • Frequently changing skincare products.

Allowing the skin to heal naturally gives the tiny blood vessels time to settle.

Support your skin barrier

A healthy skin barrier helps reduce overall irritation.

A simple skincare routine usually includes:

  • Gentle cleansing.
  • Regular moisturising.
  • Avoiding unnecessary irritation.

Healthy skin often recovers more efficiently.

Wear sunscreen every day

Although PIE is caused by blood vessels rather than pigment, daily sun protection still supports healthy skin recovery and helps reduce further irritation from ultraviolet exposure.

Broad-spectrum sunscreen should be part of every acne skincare routine.

Treat active acne

Every new inflamed spot creates another opportunity for PIE to develop.

Managing active acne remains one of the most important ways to reduce future red marks.

How is PIE different from PIH?

Although they often appear together, PIE and PIH have different causes.

PIE PIH
Red, pink or purple Brown, tan or grey
Caused by blood vessels Caused by excess pigment
More common in lighter skin More common in deeper skin tones
Usually fades over weeks to months Often fades over several months

A simple pressure test can sometimes help distinguish between them.

If gentle pressure briefly causes the redness to fade, the mark is more likely to be PIE.

Frequently Asked Questions

Is PIE permanent?

No. PIE is a temporary change caused by visible blood vessels after inflammation and usually fades gradually over time.

How is PIE different from PIH?

PIE is caused by blood vessels and appears red or pink, while PIH is caused by increased pigment and appears brown or grey.

What makes PIE last longer?

Repeated inflammation, picking spots and harsh skincare products can all prolong recovery by continuing to irritate the skin.

Does sunscreen help PIE?

Yes. Although PIE is not caused by pigment, sunscreen supports overall skin healing and protects the skin from additional irritation.

Can treating my acne stop new PIE?

Yes. Preventing new inflammatory spots is one of the most effective ways to reduce future red marks.

Reviewed by Dr Tara Treacy, GP with a special interest in dermatology (IMC 411337).

Last reviewed: 16/07/2026.

General information only. It does not replace an individual medical assessment.