PIE vs PIH: Why Red Marks and Brown Marks Fade Differently

PIE vs PIH comes down to what is making the color. PIE, post-inflammatory erythema, is a flat pink, red, or purple mark caused by widened small blood vessels. PIH, post-inflammatory hyperpigmentation, is a flat brown or gray mark caused by extra melanin. Neither is a scar, and both usually fade on their own. This guide covers how to tell them apart, why each one responds to different things, and the signs that a mark is turning into a scar.

What is the difference between PIE and PIH?

Both are what a blemish leaves behind once the inflammation is over. The difference is the material you are looking at.

PIH is a pigment problem. A 2018 review defines it as a reactive hypermelanosis that develops following cutaneous inflammation, from acne, eczema, burns, or skin procedures. In acne, the inflammation stimulates excess melanin production and abnormal melanin deposition. The extra pigment stays behind after the pimple is gone.

PIE is a blood vessel problem. A 2022 review of the laser literature describes post-acne erythema as redness from inflammatory signals, dilated microcapillaries in the papillary dermis, and a thinned epidermis. Nothing extra has been deposited. You are seeing blood through the skin.

The term PIE is newer than most people assume. It was proposed in 2013 because no term existed for pink to red discoloration after an inflammatory acne lesion. The vocabulary is still unsettled. The American Academy of Dermatology patient page files red or pink post-acne spots in lighter skin under PIH, with brown or bluish gray spots in medium and darker skin. A 2021 expert panel recommended new names altogether: acne-induced macular erythema and acne-induced macular hyperpigmentation. When two sources seem to disagree, check which color they mean.

PIE vs PIH at a glance

	PIE	PIH
What it is	Widened small blood vessels near the surface	Extra melanin in the epidermis, the dermis, or both
Usual color	Pink, red, or purple	Tan, brown, or gray-blue
Press on it	Pales briefly, then returns	Stays the same
More common in	Lighter skin	Darker skin
Typical course	Fades over months, sometimes longer	Light spots often fade in 6 to 12 months, deep pigment can take years
What acts on it	Time, and vascular treatments in a clinic	Sun protection, pigment-directed topicals, time

The skin tone split comes from a 2021 working group on acne pigment. It found PIH more common in darker skin and PIE in lighter skin, and noted that both can be long lasting. Patients often find the marks more distressing than the acne itself.

How to tell PIE from PIH at home

Press test. Press the side of a clear drinking glass against the mark and look through it. Redness that comes from blood in widened vessels usually pales under pressure, because the pressure pushes blood out of them. Melanin sits inside skin cells and does not move. Clinicians use a formal version called diascopy, a clinical test for blanching that shows whether a lesion is vascular. At home it is a rough guide, not a diagnosis.

Color, adjusted for skin tone. Pink and red usually mean PIE. Brown usually means PIH. The rule weakens on darker skin. Panelists in that 2021 consensus noted that acne-induced erythema might take a different hue in darker skin, such as purple or brown. That is exactly where the press test earns its place.

Both at once. The same face often carries both. The clinical trials below tracked PIE lesions and PIH lesions separately in the same patients.

Run a finger over it. A flat mark is a color change. A dip, a pit, or a raised bump is a change in structure, which makes it a scar. Our guide to the types of acne scars shows how to check in side light.

One more check for brown. PIH sits exactly where a blemish or injury was. A symmetrical brown patch across both cheeks is a different pattern, and melasma vs hyperpigmentation explains why that matters.

Why red marks and brown marks respond to different things

A treatment works on a target. PIE and PIH have different targets.

Most brightening ingredients act somewhere on the melanin pathway. Niacinamide is a good example. In lab models it produced 35 to 68 percent inhibition of melanosome transfer from pigment cells to skin cells. In clinical tests in Japanese women it reduced hyperpigmentation compared with vehicle after 4 weeks. None of that acts on a widened capillary. An ingredient that only works on melanin has nothing to work on in a pink mark.

PIE needs something that acts on the vessels, or on the inflammation keeping them open. In clinics that usually means light. The paper that named PIE describes the 595 nm pulsed dye laser as targeting hemoglobin to treat small-diameter vascular processes. Hemoglobin is the pigment in blood, so the laser aims at the vessel rather than the melanin.

Depth decides a lot for PIH. A 2017 review calls the depth of melanin pigment the key factor to predict prognosis, and notes that epidermal pigment fades faster than dermal pigment. The AAD puts it in plain numbers. A spot a few shades darker than your skin usually fades within 6 to 12 months. Pigment that lies deep, often slate blue to gray, can take years.

What helps PIH, and how strong is the evidence?

Sun protection comes first. A 2023 review found that UV can induce PIH and PIE, and that sunscreens can prevent post-inflammatory hyperpigmentation. It also found only four relevant studies. The advice is confident. The evidence under it is thin.

Visible light matters in darker skin. In 20 volunteers with skin types IV to VI, visible light produced pigmentation that was darker and more sustained than long-wavelength UVA. Skin type II showed no pigmentation at all. A 2021 review notes that ordinary broad-spectrum sunscreens do not adequately protect against visible light. Tinted formulas built with iron oxides do, which is why the review calls them beneficial for hyperpigmentation disorders such as postinflammatory hyperpigmentation. The AAD notes that iron oxide is listed among a sunscreen's inactive ingredients, not the active ones.

Topicals. Treatment begins with managing the acne itself. First-line therapy is then a topical depigmenting agent plus sunscreen. Options named in that review include azelaic acid, retinoids, and niacinamide. Tretinoin has one of the older controlled trials. In 54 Black patients over 40 weeks, 0.1 percent tretinoin lightened PIH lesions by 40 percent toward normal skin color, against 18 percent with vehicle cream. Half of the tretinoin group developed retinoid dermatitis. Irritation is inflammation too, so a harsh routine can feed the problem it is meant to fix. Tranexamic acid is another option with a growing literature, covered in tranexamic acid in skincare.

Keep expectations modest. A 2024 systematic review pooled 41 studies and 877 patients. Complete clearance was uncommon: 5.4 percent with topicals and 18.1 percent with lasers and energy-based devices. Partial response was common, at 72.4 percent with topicals. In 2.6 percent of laser-treated patients, PIH got worse.

What helps PIE, and how strong is the evidence?

Time. PIE usually fades on its own, but a 2022 review notes it can persist for months. A 2026 review says both kinds of acne mark can persist for months or even years.

Light and lasers. A 2022 systematic review screened 5,796 records and included 18 studies. Light and laser devices were the most studied, with pulsed dye lasers used most often. The authors found no gold standard treatment and called for more randomized trials.

Topicals, on small evidence. The same review called topical oxymetazoline, tranexamic acid, and brimonidine promising. For tranexamic acid, most of the evidence is small. A 2024 review links its use in post-acne erythema to anti-inflammatory and anti-angiogenic effects. It cites a report in which a topical solution applied nightly reduced erythema. The original is a two-page case report, not a controlled trial.

One placebo-controlled trial stands out. Of 72 patients with mild to moderate acne, 60 finished 12 weeks of 15 percent azelaic acid gel or placebo gel, twice daily. The azelaic group showed significantly reduced PIE scores compared with placebo at weeks 8 and 12, and lower hemoglobin readings in treated PIE lesions. PIH lesions improved in both groups. Brown marks fade with time alone, and any study without a placebo arm will miss that. Our azelaic acid guide explains why the strength on the label matters.

When a red or brown mark is becoming a scar

Most marks fade. A few do not stay flat.

A prospective study followed 32 people with moderate acne and existing scars for 6 months, mapping their lesions twice a week at first. Nearly all new atrophic scars, 83 percent, arose from erythematous macules or hyperpigmentation rather than straight from a pimple. Of the scars still present at 6 months, 81.7 percent were still there at 2 years. The authors advise clinicians to monitor patients with macular erythema closely for scarring.

So check your marks in side light every few weeks. A mark that is sinking below the surrounding skin is a reason to see a board-certified dermatologist. The 2021 expert panel states that early, effective treatment can potentially limit and prevent sequelae, and its recommendations rest on expert opinion rather than high-quality trials.

Habits that make both marks last longer

• Picking. A 2026 review lists traumatized lesions, excessive sunlight exposure, and darker skin color among the important risk factors for acne-induced pigment. The AAD warns that picking, popping, or squeezing acne increases your risk of getting a scar.
• Leaving the acne untreated. Each new blemish can leave a new mark. The AAD says the skin condition must be treated first for hyperpigmentation to clear.
• Irritating products. The same AAD page notes that a product that irritates your skin can cause dark spots, and advises stopping anything that burns or stings.
• Aggressive procedures. PIH is one of the most common complications of procedures using lasers and other light sources, and it occurs more often in darker skin.

None of these are dramatic. Together they decide whether a mark fades in months or lingers for a year.

Frequently asked questions

Is PIE or PIH a scar?

No. Both are flat changes in color on skin that is structurally intact, and both usually fade without treatment. A scar is a change in structure, such as a dip, pit, or raised bump you can feel. A flat mark that starts to sink below the surface is worth showing to a dermatologist.

How long does PIE last?

There is no fixed timeline. PIE usually fades on its own over months, and some marks persist much longer. Sun protection and leaving the area alone help. When PIE persists, the most studied treatments are vascular lasers and light devices used in a clinic.

How long does PIH take to fade?

According to the American Academy of Dermatology, a spot a few shades darker than your skin usually fades within 6 to 12 months once the cause has stopped. Pigment that lies deep in the skin, often slate blue to gray, can take years. Daily sun protection and not re-injuring the area both matter.

Will a brightening serum fade red marks?

Usually not by itself. Most brightening ingredients act on melanin, and a red mark is made of dilated blood vessels rather than pigment. A few ingredients with anti-inflammatory actions, such as azelaic acid, have small trials in red marks. Vascular lasers remain the most studied option.

Can you have PIE and PIH at the same time?

Yes. The same face often carries both, and studies track them as separate lesions in the same patients. On darker skin, PIE can look purple or brown, which makes it easy to mistake for pigment. Pressing a clear glass against the mark helps, since vascular redness pales under pressure and pigment does not.

When should I see a dermatologist about acne marks?

See a board-certified dermatologist if a mark is sinking or raised, if new marks keep appearing because the acne is not controlled, or if brown patches appear symmetrically without any blemishes first. Those patterns point to scarring, active disease, or a different pigment condition. A correct diagnosis changes the plan.

Related reading: How to fade dark spots.