TL;DR: If your acne fades but leaves marks, those marks are one of two completely different things, and the treatments don't overlap. Most people get this wrong.
Quick answer
Acne marks come in two flavors. PIE — post-inflammatory erythema — is red, pink, or purple. PIH — post-inflammatory hyperpigmentation — is brown, gray, or dark. PIE is dilated blood vessels left behind by inflammation. PIH is excess melanin deposited in the area where a pimple sat. They look different, last different lengths of time, and respond to completely different treatments. Brightening serums won’t fade PIE. Redness products won’t fade PIH. Knowing which you have is step one.
How to tell them apart
PIE shows up as flat red, pink, or purplish marks where pimples used to be. Press a clear glass slide or your fingertip to the mark and watch — if the redness briefly fades under pressure, it’s PIE. The vessels are dilated and the blood is moveable. PIE is more common in lighter skin tones (Fitzpatrick I through III).
PIH shows up as flat brown, gray, or dark spots. The pigment doesn’t move with pressure because it sits deeper in the skin. PIH is more common in deeper skin tones (Fitzpatrick IV through VI), but it can happen at any skin tone.
You can have both on the same face. Plenty of people do. The treatment plan has to address each one separately.
Why they’re different
PIE happens when inflammation damages the small dermal blood vessels and leaves them dilated near the surface. The redness fades as the vessels gradually settle back to normal — usually six to twelve months without intervention, faster with the right treatment.
PIH happens when inflammation tells melanocytes to overproduce melanin, and the pigment deposits in the surrounding skin. It fades as cell turnover slowly carries the pigment up and sheds it — usually six months to two years without intervention, faster with the right protocol.
Neither one is true scarring. True scarring is textural — depressed, raised, or stretched. PIE and PIH are flat. They both fade. The mistake is treating them the same way.
How to treat PIE
The goal is to support turnover, lower inflammation, and let the dilated vessels settle.
The ingredient list that actually works on red marks: niacinamide at 5 to 10 percent for anti-inflammatory action, centella asiatica for the same reason, azelaic acid at 10 to 20 percent for redness reduction, vitamin C as an antioxidant and vessel-support active, topical tranexamic acid for its emerging evidence on the vascular side.
For professional treatments, pulsed dye laser is the most effective option — one to three sessions usually does serious damage to PIE. IPL is slower and less precise. LED red light is supportive but slow.
Strong AHAs and BHAs alone won’t fade PIE much. Brightening-focused products won’t help either; this isn’t a pigmentation problem.
How to treat PIH
The goal is to slow melanin overproduction and accelerate turnover to bring the deeper pigment up and out.
Vitamin C at 10 to 20 percent inhibits tyrosinase, the enzyme that makes melanin. Niacinamide at 5 to 10 percent blocks melanin from transferring to the surface cells. Tranexamic acid at 2 to 5 percent interrupts the melanin production pathway. Azelaic acid at 10 to 20 percent is anti-inflammatory plus a tyrosinase inhibitor — the closest thing to a single ingredient that handles both ends. Retinoids speed turnover. Alpha arbutin, kojic acid, and licorice root extract are the supporting brighteners. Hydroquinone at 2 to 4 percent is the strongest, prescription-strength in most regions.
For professional treatments, chemical peels — TCA, glycolic, Jessner’s — work. Microneedling has moderate efficacy, especially when paired with serum. Q-switched lasers handle stubborn PIH but need caution in deeper skin tones. Tranexamic acid microinjections are increasingly used for melasma-adjacent PIH.
Redness-targeted products won’t shift PIH meaningfully. Different mechanism.
The timeline
Both fade slowly. Set the expectation now.
PIE typically shows visible improvement in 8 to 16 weeks of treatment and substantial fading at six months. Lasers can get you 50 percent or more in one to three sessions.
PIH typically improves in 12 to 24 weeks of consistent treatment. Stubborn or deep PIH can take 12+ months. PIH in deeper skin tones often takes longer; the pigment is denser to begin with.
Daily SPF is non-negotiable for both. PIH actively worsens with every UV exposure. PIE recovery slows without sun protection.
The protocol when you have both
For most people, after moderate acne, the marks are mixed. The routine that handles both:
AM: gentle cleanser, vitamin C 10 percent, niacinamide 5 to 10 percent, moisturizer, SPF 30+.
PM: gentle cleanser, tranexamic acid plus niacinamide serum, retinoid alternated with azelaic acid on opposite nights, moisturizer.
Weekly: mild AHA exfoliation once or twice, on non-retinoid nights.
Daily, non-negotiable: SPF 30 or higher, broad-spectrum.
Give the protocol 12 weeks before deciding it isn’t working. Patience is half the treatment.
When to see a dermatologist
PIE that hasn’t faded after 12+ months. PIH from severe acne, especially in deeper skin tones where the pigment goes deeper. Persistent marks that resist consistent OTC treatment. Anything that looks textural rather than just discolored — that’s not PIE or PIH anymore.
A derm can prescribe stronger options (tretinoin, hydroquinone) and offer in-office treatments that meaningfully shorten the fading window.
Mistakes worth avoiding
Using brightening products for PIE. Vitamin C helps PIE indirectly, but the response is mostly vascular. Tyrosinase inhibitors aren’t going to do much for dilated vessels.
Stopping treatment when the marks are “almost faded.” The last 20 percent of fading usually takes longer than the first 80 percent. Stay consistent.
Skipping SPF because the marks are already there. They get worse with UV, and the work you’re doing slows down.
Picking at marks. Every pick re-injures the area and restarts the inflammation cycle.
Believing they’re permanent scars. Most aren’t. True scars have texture; flat marks change only in color, and they will fade.
Frequently asked questions
Can I have PIE and PIH at the same time? Yes, all the time. Both protocols at once.
Does diet help? Modest evidence for anti-inflammatory eating supporting recovery. Not a substitute for the topical work.
Are pimple patches useful? Yes, especially for prevention — keeping a healing pimple covered reduces picking and lowers the inflammation that creates marks in the first place.
How do I know if it’s a true scar? True scars have texture — depressed (atrophic), raised (hypertrophic), or stretched. Flat marks that change only in color are PIE or PIH.
Sources
Bae-Harboe YS, Graber EM. Easy as PIE (postinflammatory erythema). Journal of Clinical and Aesthetic Dermatology, 2013. Davis EC, Callender VD. Postinflammatory hyperpigmentation. Journal of Clinical and Aesthetic Dermatology, 2010.
Keep reading
Keep reading
- Acne Scars (PIE & PIH)Atrophic acne scars: causes, treatment, and realistic expectations
- HyperpigmentationMelasma: why it’s stubborn and what’s new in 2026
- Acne & BreakoutsFungal acne (Malassezia): why your acne treatments aren’t working