PIH vs PIE: Understanding the Marks Acne Leaves Behind

One of the most common concerns after acne has cleared is that the marks remain. Many people assume these marks are scars, but in most cases they are not. The good news is that flat red or dark marks left behind after acne usually improve over time.

The two most common types of post-acne marks are:

Post-Inflammatory Hyperpigmentation (PIH) – dark brown, grey or tan marks.
Post-Inflammatory Erythema (PIE) – pink, red or purple marks.

Understanding which type you have helps set realistic expectations and explains why your marks look the way they do.

What is PIH?

Post-Inflammatory Hyperpigmentation (PIH) is a flat area of darker skin that develops after inflammation.

When an inflamed spot heals, the skin may produce excess melanin, the pigment responsible for skin colour.

This leaves behind a flat mark that may appear:

Brown.
Tan.
Grey.
Darker than your surrounding skin.

Importantly, the skin's surface remains smooth. Only the colour has changed.

PIH is particularly common in people with medium to deeper skin tones.

What is PIE?

Post-Inflammatory Erythema (PIE) appears differently.

Instead of increased pigment, PIE results from small blood vessels remaining visible after inflammation.

These marks are typically:

Pink.
Red.
Purple.

Again, the skin remains completely flat.

PIE is generally more noticeable in lighter skin tones because redness is easier to see.

How can I tell the difference?

A simple test can often help.

Press gently on the mark using either:

A clean fingertip.
The side of a clear drinking glass.

If the mark briefly becomes lighter before returning to its original colour, it is more likely to be PIE, because the redness comes from tiny blood vessels.

If the colour stays the same when pressure is applied, it is more likely to be PIH, where pigment rather than blood vessels is responsible.

Many people actually have both PIH and PIE at the same time, particularly after prolonged acne.

Are PIH and PIE acne scars?

No.

This is one of the biggest misconceptions surrounding acne.

Neither PIH nor PIE is considered true scarring.

The key difference is:

PIH and PIE

Flat.
Colour changes only.
Skin texture remains normal.
Usually improve with time.

True acne scars

Changes in skin texture.
Pits, depressions or raised areas.
Much slower to improve naturally.
Often require separate assessment.

Understanding this distinction can provide enormous reassurance, as most post-acne marks gradually fade.

What helps PIH and PIE fade?

Although they usually improve naturally, there are several ways to support the healing process.

Daily sun protection

Sun exposure stimulates pigment production and can significantly prolong both PIH and overall healing.

Daily broad-spectrum sunscreen is one of the most effective ways to prevent marks from becoming darker and lasting longer.

Keep your skin barrier healthy

Gentle skincare helps reduce ongoing inflammation.

Use:

A gentle cleanser.
A suitable moisturiser.
Avoid harsh scrubs.

Healthy skin heals more effectively.

Treat active acne

Every new inflamed spot has the potential to leave another mark.

Managing active acne remains one of the most important ways to prevent new PIH and PIE from developing.

Frequently Asked Questions

Will my acne marks disappear completely?

Most flat acne marks fade substantially over several months. The exact timeframe varies depending on your skin type, the amount of inflammation and how well the skin is protected from the sun.

What's the difference between PIH and PIE?

PIH is caused by excess pigment and appears brown or grey. PIE is caused by small blood vessels and appears pink or red.

Why are my marks darker than someone else's?

Skin tone plays a major role. PIH tends to be more common and longer-lasting in medium to deeper skin tones, while PIE is generally more noticeable in lighter skin.