Red or dark marks after acne are one of the most common reasons people feel their skin is not improving despite fewer breakouts. These marks often get grouped together as “scars” or “marks”, which is why many people treat them incorrectly or wonder why they are not fading. In reality, post-inflammatory erythema (PIE) and post-inflammatory hyperpigmentation (PIH) are different conditions. Whilst they both occur after acne and may look similar at first glance, they behave very differently and require different treatment approaches. Confusing them can delay recovery. In this article we explore the difference between post-inflammatory erythema vs post-inflammatory hyperpigmentation. We review how PIE and PIH develop, how to tell them apart and the best way to treat them.
What is Post-Inflammatory Erythema?
Post-inflammatory erythema occurs when inflammation due to conditions like acne or rosacea injures the small superficial blood vessels in the skin. These vessels dilate or become more fragile as the skin heals, which leaves lingering redness or pink marks after acne or irritation. Crucially, PIE is not caused by melanin, so it is not a true pigmentation issue. It is most common in lighter skin tones because redness is more visible. In general, the typical features of PIE include:
- Colour: Pink, red or purplish marks that often look worse with heat or after exercise.
- Location: Usually appears where acne lesions or irritation were present, and can occur anywhere on the face.
- Behaviour: Redness may persist for weeks or months. It often worsens with heat, over-exfoliation, barrier disruption or friction.
- Skin type: More visible in fair skin.
- Triggers: Acne, harsh skincare, procedures, picking, sunburn or any condition that disrupts the barrier.
What is Post-Inflammatory Hyperpigmentation?
Post-inflammatory hyperpigmentation occurs when inflammation prompts the colour-producing cells (melanocytes) to produce excess pigment. This leads to brown, tan or grey-blue marks which commonly appear after acne, eczema, irritation or injury. It is far more common in medium to deep skin tones, and it can be superficial or sit deeper within the skin. Typical features of PIH include:
- Colour: Brown, tan or grey-blue patches that do not turn red with heat.
- Location: Appears exactly where inflammation occurred, such as acne marks or areas of irritation.
- Behaviour: Can persist for months even when the underlying cause has settled, and improves more slowly when the pigment is deeper.
- Skin type: More common and more persistent in darker skin tones.
- Triggers: Acne, trauma, eczema flares, burns, strong acids, sun exposure or friction.
Difference Between Post-Inflammatory Erythema vs Post-Inflammatory Hyperpigmentation
Although these two conditions are different, they can look similar. To make matters more confusing, many people have both at the same time, especially after inflammatory acne. However, it’s important to try to tell them apart in order to treat them properly. Luckily there are a few clues that can help distinguish between post-inflammatory erythema vs post-inflammatory hyperpigmentation:
- Colour: PIE is usually pink or red, whereas PIH is normally brown, tan or grey.
- Blanching: PIE may temporarily lighten or disappear when you press on it. This does not happen with PIH.
- Skin tone: PIE is usually more visible in lighter skin, whilst PIH is more common in darker skin.
- Triggers: Both can follow acne, irritation or skin injury. PIH can also darken with sun exposure, whilst PIE is exacerbated by heat and friction.
- Behaviour: PIE often lingers but gradually fades as the blood vessels recover. PIH can take longer, especially if the pigment sits in deeper layers of the skin.
- Response to products: PIE does not respond to pigment inhibitors, and PIH does not respond to vascular treatments.
Correctly distinguishing PIE from PIH is essential because each responds to very different treatments. PIE is a vascular issue, so pigment suppressors and exfoliants offer little benefit and may even irritate the skin, prolonging redness. PIH, on the other hand, is driven by excess melanin and improves with pigment-suppressing skincare, gentle resurfacing and strict sun protection. Treating PIH as PIE leads to stalled progress, whilst treating PIE as PIH often causes unnecessary irritation. Both can also coexist, and irritation can worsen either one. A clear diagnosis helps you choose the right approach and avoid treatments that slow healing.
Best Treatments for Post-Inflammatory Erythema
PIE responds best to calming, vascular-focused measures rather than pigment inhibitors. It improves gradually, so expect a slow but steady reduction in redness as the skin barrier strengthens and the blood vessels repair. The best treatments for post-inflammatory erythema include:
- Barrier support: Hydrating serums and moisturisers with ceramides or fatty acids help reduce reactivity, reinforce the skin barrier and allow the vessels to recover.
- Anti-inflammatories: Niacinamide, azelaic acid or hypochlorous acid can help calm inflammation and reduce redness. This is especially valuable for managing PIE due to rosacea.
- Avoid triggers: Minimise heat, friction, over-exfoliation and harsh scrubs, which keep the vessels dilated.
- Sun protection: Heat, ultraviolet and visible light can worsen inflammation and cause flushing, so apply a daily broad-spectrum sunscreen and stay cool.
- Procedures: Vascular lasers such as pulsed dye laser or certain types of IPL (only for appropriate skin tones) can significantly reduce persistent redness.
Best Treatments for Post-Inflammatory Hyperpigmentation
PIH responds best to pigment-suppressing skincare and gentle exfoliation. However, deep PIH often takes months or even years to fade and may need a structured routine or prescription-based treatment. Useful options include:
- Pigment inhibitors: Ingredients like azelaic acid, arbutin, kojic acid, tranexamic acid, cysteamine or hydroquinone can all suppress excess melanin and fade dark marks.
- Retinoids: Over-the-counter retinoids and prescription ones like tretinoin increase cell turnover and help lift pigmented patches over time.
- Exfoliating acids: Careful use of AHAs, BHAs or PHAs can improve texture and help lift superficial pigment.
- Sun protection: Daily use of a broad-spectrum sunscreen is crucial to prevent further darkening.
- Procedures: Chemical peels and specific lasers may help with superficial PIH. However, they can cause further PIH in medium and deeper skin tones if not used correctly.
What to Do When PIE & PIH Occur Together
This is extremely common after acne. The skin may show pink marks that later settle into brown patches. When both are present, sequencing matters. Treating the acne, calming inflammation and supporting the barrier should come first. Once the redness is stable, pigment-focused treatments can be introduced gradually. Trying to treat both aggressively at the same time risks irritation, which worsens all forms of post-inflammatory marks.
Sometimes, despite your best efforts, it may not be possible to treat your post-acne marks alone. This may be because the marks are severe or not improving, or because several other things are complicating the picture. In this case, it is best to seek professional medical help, especially if:
- Redness persists beyond several months
- New marks appear without a clear trigger
- Pigmentation darkens despite sunscreen
- There is burning, scaling or discomfort
- You suspect rosacea, dermatitis or eczema
- Acne is ongoing and leaving new marks
- Pigmentation is deep, widespread or resistant to treatment
PIE and PIH may look alike, but they arise from very different processes. PIE is redness caused by vascular changes, whilst PIH is melanin-based pigmentation. Distinguishing them is essential because they need different approaches. Calming inflammation, protecting the barrier and managing acne helps prevent both. If marks persist or worsen, medical guidance can clarify the diagnosis and offer more targeted treatment.
At City Skin Clinic, we are super passionate about personalised skincare. Our virtual skin clinic offers safe and effective custom skin treatments. Where appropriate, our doctors use ingredients such as tretinoin, hydroquinone and tranexamic acid to treat conditions like acne, hyperpigmentation, melasma and skin ageing. Start your online consultation today. The journey towards great skin starts here.
This article is intended for general informational purposes only and is not a substitute for medical advice, diagnosis or treatment. Always consult a qualified medical professional with any concerns about your skin or treatment options.
