Post-Inflammatory Erythema (PIE) vs Hyperpigmentation: How to Tell Them Apart and What Actually Fades Red Acne Marks
By Dr. Mei Chen · Cosmetic Dermatologist & Senior Editor, The Exosome Edit
Updated Jun 2026When a pimple finally goes away, it often leaves a flat mark behind, and that mark is either pink-red or brown-gray. The two look similar at a glance but come from different problems in the skin, so the treatments that fade one do almost nothing for the other. Getting the diagnosis right is the single most important step, because a pigment cream on a red mark is wasted effort and a vascular laser on a brown mark is wasted money.
When a pimple finally goes away, it often leaves a flat mark behind, and that mark is either pink-red or brown-gray. The two look similar at a glance but come from different problems in the skin, so the treatments that fade one do almost nothing for the other. Getting the diagnosis right is the single most important step, because a pigment cream on a red mark is wasted effort and a vascular laser on a brown mark is wasted money.
The Two Marks Acne Leaves Behind
Acne marks fall into two main buckets, plus a third thing people often confuse with both.
Post-inflammatory erythema (PIE) is the flat pink, red, or purple mark left after a pimple. It is not a stain in the skin. It is dilated and damaged tiny blood vessels in the upper layer of skin, left over from the inflammation. When acne flares, the body floods the area with blood and inflammatory signals. Once the pimple heals, those small vessels can stay widened, and the thinned skin on top makes them easy to see. PIE shows up most in lighter skin tones, where there is less melanin to mask the redness.
Post-inflammatory hyperpigmentation (PIH) is the flat tan, brown, gray, or blue-gray mark left after a pimple. This one really is extra pigment in the skin. The inflammation switches on melanocytes, the cells that make melanin, and they overproduce it. That pigment can sit in the upper layer of skin (epidermal) or sink deeper (dermal). PIH is far more common and more stubborn in medium-to-deep skin tones. A 2010 review of pigment disorders in skin of color found that dyschromias (color changes) ranked among the most common reasons people with darker skin saw a dermatologist, and that severity tracked with how much melanin a person's skin makes, not with race itself (Davis & Callender, J Clin Aesthet Dermatol, 2010, PMID 20725554).
Acne scars are the third thing, and they are different from both. A scar is a change in the skin's texture or shape — a pit, a depression, a raised bump. PIE and PIH are flat. If you run a finger over the mark and the surface is smooth and level, you are dealing with PIE or PIH, not a scar. Scars need their own treatments (microneedling, lasers, fillers, subcision), which this article does not cover.
This distinction matters more than any product choice. The honest truth: most red and brown acne marks fade on their own over months. The reason to treat is to speed that up and to stop new marks from forming.
How to Tell PIE and PIH Apart at Home
You do not need a dermatologist to make a good first guess. Three checks get you most of the way.
The Press Test (Diascopy)
Press a clear glass or a clean fingertip firmly on the mark for a few seconds, then look as you release — or look through the glass while pressing.
- If the mark fades, blanches, or briefly disappears under pressure, it is likely PIE. You are squeezing blood out of those dilated vessels, so the color drops.
- If the mark stays the same color under pressure, it is likely PIH. Pigment does not move when you press on it.
This press test (dermatologists call it diascopy) is the most useful single trick for telling the two apart.
Color
- Pink, red, crimson, or purple points to PIE.
- Tan, brown, dark brown, gray, or blue-gray points to PIH.
Color alone is not foolproof, because some people have both at once, and lighting changes how marks look. But combined with the press test, it is reliable.
Skin Tone Context
PIE is more often the main issue in lighter skin (roughly Fitzpatrick types I–III). PIH dominates in medium-to-deep skin (types IV–VI), where melanocytes react more strongly to inflammation. People in the middle can get both — a red mark that slowly turns brown as it ages.
| Feature | PIE (Post-Inflammatory Erythema) | PIH (Post-Inflammatory Hyperpigmentation) |
|---|---|---|
| Color | Pink, red, purple | Tan, brown, gray, blue-gray |
| What it actually is | Dilated/damaged blood vessels | Excess melanin pigment |
| Press test (diascopy) | Fades / blanches when pressed | Stays the same when pressed |
| Most common in | Lighter skin (types I–III) | Deeper skin (types IV–VI) |
| Texture | Flat, smooth | Flat, smooth |
| Makes it worse | Heat, irritation, sun, harsh actives | Sun, visible light, picking, irritation |
| Best-evidence treatments | Vascular lasers (PDL), IPL; time | Sunscreen, retinoids, azelaic acid, hydroquinone, tranexamic acid |
| Typical fade time, untreated | Weeks to many months | Months to years |
If you are unsure, or if marks have lasted longer than a year, see a board-certified dermatologist. Misdiagnosing the two is the most common reason people waste time and money on the wrong products.
Why the Treatments Are Completely Different
The split comes down to the target. PIE is a blood vessel problem. PIH is a pigment problem. A treatment that shrinks blood vessels does nothing to melanin, and a melanin-blocking cream does nothing to a dilated capillary.
There is one rule both conditions share, and it is the most important rule in this entire article: stop the inflammation and stop the sun. Both marks are caused by inflammation, so controlling active acne is step one. And both get worse with ultraviolet and visible light. Daily broad-spectrum sunscreen is non-negotiable for either condition — for PIH especially, sun and even visible light from the sky and screens can deepen the pigment and stall any treatment. (More on what level of SPF actually matters in our SPF 30 vs higher evidence review.)
Picking, squeezing, and scrubbing make both worse by adding more inflammation. The single best "treatment" for acne marks is preventing them: get the acne under control early, keep your hands off, and wear sunscreen.
What Actually Fades PIE (Red Marks): The Evidence
Here is the uncomfortable part. The evidence for PIE treatment is thinner than most blog posts admit. The best-supported options are in-office lasers, and even those rest on small studies.
Vascular Lasers (Pulsed Dye Laser) — Best Evidence, Still Limited
The pulsed dye laser (PDL, usually 595 nm) targets hemoglobin in blood vessels. The light heats and collapses the dilated capillaries that cause the redness, without harming surrounding skin much. This is the standard tool for vascular redness, and it is the most-studied option for PIE.
A 2008 pilot study treated patients with acne-related redness using a long-pulsed 595 nm PDL over two sessions and reported clinical improvement with minimal discomfort (Acne erythema improvement by long-pulsed 595-nm pulsed-dye laser, J Dermatolog Treat, 2008, PMID 18273723). A widely cited case report series in 2013, titled "Easy as PIE," helped define post-inflammatory erythema as its own entity and showed two patients improving with 595 nm PDL — while the authors openly stated that "further studies are needed to establish safety, define optimal laser settings, and quantify effectiveness" (Bae-Harboe & Graber, J Clin Aesthet Dermatol, 2013).
Honest grade: moderate-to-weak. PDL is the best tool we have for PIE, and dermatologists use it because the mechanism is sound and results are real in practice. But the published evidence is pilot studies and case reports, not large randomized trials. Expect to need multiple sessions, and expect to pay out of pocket.
Intense Pulsed Light (IPL)
IPL uses a broad band of light rather than a single laser wavelength, and it can hit both red (vessels) and brown (pigment) targets. That makes it appealing when someone has a mix of PIE and PIH. A 2022 retrospective study of 60 Chinese patients with acne-induced PIE and PIH found that about 81.7% achieved complete or partial clearance, with significant drops in both redness and brown-spot measurements on imaging, and only short-lived side effects (Wu et al., Dermatol Ther, 2022, PMID 35415801).
Honest grade: moderate. The dual action is a genuine advantage for mixed marks, but this is a retrospective study from a single population, not a randomized trial. IPL is operator-dependent and not ideal for very deep skin tones, where it can cause burns or pigment changes.
Topicals for PIE — Weak Evidence
Plenty of topical ingredients get marketed for red marks: brimonidine (constricts vessels temporarily), niacinamide, azelaic acid, vitamin C, and low-strength retinoids. The reality is that most of these have little direct trial evidence for PIE specifically, and several can backfire. Strong retinoids and acids can irritate skin that is already red, making PIE look worse before it gets better. Brimonidine only narrows vessels for a few hours and can cause rebound redness.
Honest grade: weak. If you want to try a topical, niacinamide and gentle azelaic acid are the low-risk choices, but manage expectations. For PIE, the most powerful "topical" is time plus sunscreen plus not irritating the skin.
What Actually Fades PIH (Brown Marks): The Evidence
PIH has a much deeper evidence base than PIE, because pigment disorders have been studied for decades. The catch: most studies are small, many come from melasma research (a related but different condition), and improvements are gradual.
Sunscreen — The Foundation
This is not optional and it is not a "nice to have." Sun and visible light directly drive melanin production. Without daily broad-spectrum sunscreen, every other PIH treatment is fighting uphill. Reviews of PIH in skin of color list strong photoprotection as first-line, alongside any active ingredient (Davis & Callender, 2010, PMID 20725554). Tinted mineral sunscreens with iron oxides add visible-light protection, which matters more for deeper skin tones.
Retinoids — Strong Evidence
Topical retinoids (tretinoin, adapalene, tazarotene) speed cell turnover and help disperse pigment, and they also treat the underlying acne that causes new marks. Across PIH reviews, retinoids consistently show meaningful pigment reduction, especially in skin of color, and they are a backbone of treatment. Honest grade: strong for the class, though they can irritate and briefly worsen redness, so start low and slow.
Azelaic Acid — Good Evidence, Gentle
Azelaic acid blocks an enzyme involved in melanin production and calms inflammation, so it treats both the pigment and the acne. A 2023 single-blind randomized trial compared 20% azelaic acid cream against 5% tranexamic acid solution for acne-related PIH over 12 weeks; both groups improved significantly on a post-acne hyperpigmentation index, with good tolerability (Sobhan et al., J Res Med Sci, 2023, PMID 37213446). Azelaic acid is a strong choice for sensitive skin and is safe in pregnancy. We cover it in depth in our azelaic acid research review.
Hydroquinone — The Most-Studied Lightener
Hydroquinone blocks melanin production directly and is the most-studied topical for pigment, often used at 4% by prescription or in "triple combination" with a retinoid and a mild steroid. It works, but it is meant for short courses under guidance, not endless daily use, because long-term overuse can cause its own pigment problem (ochronosis). Honest grade: strong, with the caveat that it needs a clear stop date and dermatologist oversight.
Tranexamic Acid — Promising but Mixed
Tranexamic acid (TXA) comes as a topical, an oral pill, or an in-office injection, and it interferes with the signaling between skin cells and melanocytes. A 2022 systematic review of TXA for PIH pooled 9 studies and 196 patients and concluded that oral, topical, and intradermal forms all reduced pigmentation, but the studies used different doses, follow-up windows, and scoring systems, which limited firm conclusions (Alsharif et al., Clin Cosmet Investig Dermatol, 2022, PMID 36597522). Honest grade: moderate and mixed. Topical TXA is a reasonable low-risk add-on; oral TXA should only be used under medical supervision because of clotting concerns. See our tranexamic acid serum review for the topical side.
Other Options
Vitamin C, niacinamide, kojic acid, alpha arbutin, and cysteamine all show some pigment-fading signal, mostly modest and mostly from small studies. Chemical peels (glycolic, salicylic, mandelic) and lasers can help deeper PIH but carry a real risk of causing more PIH in deeper skin tones if done too aggressively. For a ranked breakdown, see our guide to evidence-based hyperpigmentation ingredients.
| Treatment | Targets | Evidence grade | Best for | Watch-outs |
|---|---|---|---|---|
| Daily sunscreen | Both (prevents worsening) | Strong (foundation) | Everyone | Reapply; tinted helps deep skin |
| Pulsed dye laser (PDL) | PIE (vessels) | Moderate–weak | Red marks, lighter skin | Multiple sessions, cost |
| IPL | Both | Moderate | Mixed red + brown | Risky in deep skin tones |
| Topical retinoids | PIH (pigment) + acne | Strong | Brown marks | Irritation; can flare PIE |
| Azelaic acid | PIH + acne | Good | Sensitive skin, pregnancy | Slow; mild tingling |
| Hydroquinone | PIH | Strong (short-term) | Stubborn brown marks | Needs stop date; Rx |
| Tranexamic acid | PIH | Moderate / mixed | Add-on for pigment | Oral needs MD oversight |
| Vitamin C, niacinamide | PIH (mild) | Weak–moderate | Maintenance, support | Modest effect alone |
Mixed Marks and Real-World Routines
Plenty of people have both PIE and PIH on the same face, or a mark that started red and is turning brown. When the two coexist, the practical move is to treat the underlying acne first, protect from sun, and then pick a strategy that covers both — IPL in-office, or a gentle topical routine that fades pigment without inflaming the redness.
A reasonable at-home starting routine for mixed marks: a gentle cleanser, a non-irritating pigment-fading active like azelaic acid or low-dose niacinamide in the morning, a retinoid at night (started slowly), and broad-spectrum sunscreen every single morning. Keep active acne controlled, because every new pimple makes a new mark. Our breakdown of salicylic acid vs benzoyl peroxide vs azelaic acid can help you pick an acne active that won't over-irritate.
Safety and Who Should See a Dermatologist
A few safety points apply across the board:
- Don't pile on actives. Stacking strong retinoids, acids, and benzoyl peroxide at once usually causes more irritation, which causes more PIE and PIH. Less is more.
- Patch test new products, especially hydroquinone and high-strength acids.
- Deep skin tones need caution with procedures. Aggressive peels and lasers can trigger new PIH. Choose a provider experienced with your skin tone.
- Hydroquinone is not for indefinite use. Use it in short, supervised courses.
- Oral tranexamic acid carries clotting risk and is only for people cleared by a doctor.
See a board-certified dermatologist if: marks have lasted more than a year, you cannot tell whether you have PIE, PIH, or scarring, your acne is still active and severe, the marks are spreading or changing, or over-the-counter options have failed after a few months. A dermatologist can confirm the diagnosis, prescribe stronger options, and tailor laser settings to your skin tone safely.
Who Each Approach Is For
If your marks are pink/red and blanch when pressed (PIE): Your most effective options are in-office vascular treatments (PDL or IPL). At home, focus on calming the skin, avoiding irritation, daily sunscreen, and patience. Don't waste money on pigment-lightening creams — they target the wrong thing.
If your marks are brown/gray and don't blanch (PIH): Topicals do real work here. Build around sunscreen, a retinoid, and azelaic acid, with hydroquinone or tranexamic acid as next steps for stubborn marks. This is a months-long project, not a quick fix.
If your marks are pitted or raised (scars): Neither approach above will help much. You need scar-specific treatments, and that conversation belongs with a dermatologist.
For everyone: Prevention beats treatment. Control the acne, keep your hands off your face, and wear sunscreen daily. That trio prevents more marks than any serum on the shelf.
Frequently Asked Questions
How do I know if I have PIE or PIH?
Press a clear glass or your fingertip firmly on the mark. If it fades or disappears under pressure, it is likely post-inflammatory erythema (PIE), which is dilated blood vessels. If it stays the same color, it is likely post-inflammatory hyperpigmentation (PIH), which is excess pigment. Color is a second clue: red and pink point to PIE, while brown and gray point to PIH. If the mark is pitted or raised rather than flat, it is a scar, not a flat mark.
Will my acne marks go away on their own?
Usually, yes — but slowly. PIE (red marks) often fades over weeks to many months as the blood vessels recover. PIH (brown marks) can take months to years, especially in deeper skin tones and deeper pigment. Treatment speeds this up and prevents new marks, but the honest truth is that time plus sun protection does most of the work for many people.
Can the same product treat both red and brown marks?
Mostly no, because they have different targets. Red marks are a blood vessel problem and brown marks are a pigment problem. The two exceptions that touch both are daily sunscreen, which prevents worsening of either, and IPL in-office treatment, which uses broad-spectrum light to hit both vessels and pigment. For at-home care, you generally need different ingredients for each, and gentle multitaskers like azelaic acid and niacinamide are the safest bet when you have both.
Do retinoids help red marks or just brown ones?
Retinoids have strong evidence for fading brown marks (PIH) and for treating the acne that causes all marks. For red marks (PIE), the evidence is weak, and strong retinoids can actually irritate already-red skin and make redness look worse at first. If you have mostly PIE, introduce retinoids slowly and low-strength, and lean on vascular treatments instead.
Is sunscreen really that important for fading acne marks?
Yes, and it is arguably the single most important step. Both ultraviolet and visible light worsen pigment and prolong redness. Without daily broad-spectrum sunscreen, every other treatment works against the clock. For deeper skin tones, a tinted mineral sunscreen with iron oxides adds protection against visible light, which plain sunscreens miss. Skipping sunscreen is the most common reason marks refuse to fade.
This article is for general information and is not medical advice. Acne marks and pigment disorders vary widely between people and skin tones — consult a board-certified dermatologist for diagnosis and a treatment plan suited to your skin.