Acne often leaves visible changes on the skin even after active spots have healed. Some of these changes fade on their own, while others persist for months. If you notice red or brown marks and wonder whether they are scars or just temporary discolouration, you are not alone.
Post-acne marks are usually flat colour changes that fall into two categories: post-inflammatory erythema (PIE), which appears red or pink, and post-inflammatory hyperpigmentation (PIH), which looks brown or grey. These are different from acne scars, which cause permanent texture changes such as pits or raised tissue. If you would like a deeper breakdown, see our guide on acne marks vs acne scars.
Knowing whether you have PIE, PIH, or scars not only clears up the confusion but also helps you choose the most effective treatment pathway.
PIE vs PIH: How to Tell the Difference
Both post-inflammatory erythema (PIE) and post-inflammatory hyperpigmentation (PIH) can appear once acne heals. They are flat marks, not scars, but develop through very different processes in the skin. Recognising which one you have matters because the treatments that improve PIE are not the same as those that target PIH.
What Is Post-Inflammatory Erythema (PIE)?
- Cause: Inflammation damages or dilates tiny blood vessels close to the skin’s surface.
- Appearance: Pink, red, or purplish flat patches; most noticeable in lighter skin tones.
- Diagnostic cue: Often lightens temporarily when pressed (the blanch test).
What Is Post-Inflammatory Hyperpigmentation (PIH)?
- Cause: Inflammation stimulates melanocytes (pigment-producing cells) to release excess melanin.
- Appearance: Brown, grey, or bluish flat patches; more common in medium to darker skin tones.
- Diagnostic cue: Does not change colour when pressed.
Side-by-Side Comparison
| Feature | PIE (Post-Inflammatory Erythema) | PIH (Post-Inflammatory Hyperpigmentation) |
|---|---|---|
| Underlying change | Dilated or damaged blood vessels | Excess melanin pigment |
| Colour | Pink, red, or purplish | Brown, grey, or bluish |
| Texture | Flat, smooth | Flat, smooth |
| Blanch test | Lightens when pressed | No change when pressed |
| Skin types affected | All types; more visible in lighter tones | More common in medium to darker tones |
| Common triggers | Inflammation, skin picking, heat, flushing | Inflammation, UV exposure, trauma, hormones |
| Treatment focus | Vascular-targeted care (e.g. certain laser therapies) | Pigment-targeted care (topicals, peels, pigment lasers) |
Getting the classification right ensures that treatment targets the root cause of the mark, improving results and preventing wasted time on ineffective options.
Can PIE and PIH Occur Together?
Yes. The same acne lesion can leave behind both redness (PIE) and pigmentation (PIH).
- A red mark forms when blood vessels are injured.
- The same site may also produce excess melanin, creating brown or grey discolouration.
- Mixed marks often appear red and brown at once, and are especially noticeable in medium to darker skin tones.
Treatment approach:
- Control active acne to prevent new marks.
- Address PIE first with vascular lasers to reduce redness.
- Follow with pigment-focused care (topicals, chemical peels, or pigment lasers) for PIH.
Treatment Options for PIE and PIH
Both post-inflammatory erythema (PIE) and post-inflammatory hyperpigmentation (PIH) may fade with time, but many people find that the marks persist without targeted treatment. Because PIE is vascular and PIH is pigmentary, the most effective approach differs.
General Care for Both PIE and PIH
A supportive routine helps protect healing skin and reduces the chance of new marks:
- Sunscreen: Broad-spectrum protection against UVA, UVB, and visible light prevents redness from worsening and pigmentation from darkening.
- Gentle cleansing and moisturising: Maintain the skin barrier and reduce ongoing irritation.
- Avoid harsh products: Over-exfoliation, scrubbing, or alcohol-heavy toners can aggravate fragile vessels and trigger pigmentation.
- Control active acne early: Reduces repeated inflammation and lowers the risk of both PIE and PIH.
PIE-Specific Treatments
PIE develops from dilated or damaged blood vessels, so treatment focuses on vascular changes.
Vascular Laser Treatments
Lasers are the main medical approach for PIE. They deliver light energy absorbed by haemoglobin (the red pigment in blood), which shrinks dilated capillaries and reduces visible redness. Most patients need multiple sessions spaced 4–6 weeks apart. The choice of laser depends on skin type, severity, and depth of vessels:
| Laser type | Target | Notes |
|---|---|---|
| Pulsed Dye Laser (PDL, 585–595 nm) | Superficial red vessels | Highly effective for shallow redness in lighter skin |
| KTP Laser (532 nm) | Surface-level vascular marks | Precise for small, discrete red spots |
| Nd:YAG (1064 nm, long-pulsed) | Deeper vessels | Safer option for darker skin tones |
| Intense Pulsed Light (IPL) | Diffuse redness | Improves overall tone but less targeted than lasers |
Supportive Measures
- Topical anti-inflammatory care: Certain prescriptions may help calm residual inflammation.
- Lifestyle adjustments: Avoiding heat, alcohol, and vigorous scrubbing can reduce persistent flushing and worsening of redness.
PIH-Specific Treatments
PIH occurs when excess melanin is produced after inflammation. Management focuses on regulating and dispersing pigment.
Topical Treatments
These are often first-line and can be combined for stronger results:
| Ingredient | Role in PIH management |
|---|---|
| Retinoids | Increase cell turnover, disperse pigment |
| Azelaic acid | Reduces inflammation and melanin activity |
| Vitamin C | Antioxidant; regulates melanin production |
| Niacinamide | Slows pigment transfer between skin cells |
| Hydroquinone (prescription) | Temporarily suppresses melanin production under medical guidance |
Chemical Peels
Superficial peels encourage skin renewal and help fade pigmentation:
- Alpha hydroxy acids (AHAs): Glycolic, lactic, mandelic acid.
- Beta hydroxy acids (BHAs): Salicylic acid, useful for acne-prone skin.
- Low-strength TCA: Used cautiously for pigment control.
Peels are usually done in a series, with type and strength chosen according to skin type and PIH severity.
Pigment-Targeting Laser Treatments
For stubborn or deeper pigmentation, laser and light treatments can break down melanin granules:
- Q-switched lasers (532 nm, 1064 nm): Deliver energy to pigment clusters.
- Picosecond lasers: Ultra-short pulses with less heat spread, suitable for resistant pigmentation.
- Fractional lasers: Stimulate renewal and may help with deeper pigmentation layers.
Multiple sessions are often required, with settings adjusted carefully to reduce the risk of rebound pigmentation in darker skin tones.
Prevention Tips: Reducing Risk of PIE and PIH
While treatments can improve post-inflammatory erythema (PIE) and post-inflammatory hyperpigmentation (PIH), prevention remains the most effective way to reduce long-term marks after acne.
- Protect your skin from the sun: Apply broad-spectrum sunscreen daily and reapply every few hours when outdoors. Use hats or shade in Singapore’s strong year-round UV.
- Avoid picking or squeezing acne: Trauma increases inflammation and may leave PIE, PIH, or scars.
- Maintain a gentle routine: Use mild cleansers and regular moisturisers. Avoid harsh scrubs and over-exfoliation that can aggravate the skin.
- Control acne early: If over-the-counter options are not effective, seek timely medical care to prevent repeated inflammation and new marks.
Prevention cannot eliminate PIE or PIH completely, but these steps lower the risk and make marks easier to treat if they occur.
When to Seek Professional Help in Singapore
Some acne marks fade with time, but others persist or worsen without treatment. Professional guidance can save you time and improve outcomes.
- When marks do not fade: PIE and PIH may last months or years. If they show little change despite good skincare, medical treatment may be required.
- When you are unsure if they are marks or scars: Flat marks differ from scars, which involve texture changes such as pits or raised tissue. A doctor can provide an accurate diagnosis.
- When marks affect confidence: Persistent red or brown marks can impact daily life, including school, work, or social situations.
What to Expect During a Consultation
A consultation usually involves:
- Skin analysis under bright light or dermoscopy.
- Classification of marks, scars, or both.
- Personalised plan combining topical care and procedures tailored to your skin type and needs.
If PIE or PIH is persistent, confusing, or affecting your quality of life, a professional evaluation can provide clarity and next steps. At Sozo Clinic, Dr. Justin Boey provides medical assessment and recommends treatments suited to different skin types and acne-related concerns.
Frequently Asked Questions (FAQs)
How long do PIE and PIH take to fade?
Milder marks may improve in months, but deeper pigmentation or persistent redness can last for years without treatment.
Can PIE turn into PIH?
Yes. A red mark may darken into pigmentation if inflammation continues or if the skin is exposed to UV light.
Do PIE and PIH always need professional treatment?
Not always. Some marks fade naturally, but persistent or widespread ones often benefit from medical care.
Are PIE and PIH the same as acne scars?
No. PIE and PIH are colour changes, while scars involve changes in texture. Scars require texture-focused treatments.
Conclusion: Next Steps for Treating PIE and PIH
Post-inflammatory erythema (PIE) and post-inflammatory hyperpigmentation (PIH) are common after acne, but they arise from different causes — PIE from changes in blood vessels, and PIH from excess pigment. Both are flat marks, not scars, and each requires a different approach to treatment.
Daily habits such as sun protection, gentle skincare, and early acne control reduce the chance of new marks forming. When PIE or PIH persist, options such as vascular lasers, pigment-regulating topicals, chemical peels, or pigment-targeting lasers may be considered.
If you are unsure whether your marks are redness, pigmentation, or scarring, seeking professional care in Singapore can provide clarity. A doctor can distinguish between them, recommend a tailored treatment plan, and help you move forward with confidence.
