Post-Inflammatory Hyperpigmentation: How to Fade Dark Acne Marks

Post-inflammatory hyperpigmentation (PIH) is the flat brown, grey or dark mark a pimple leaves behind, and it’s especially common in medium and dark skin. It isn’t a scar: shallow PIH usually fades within 6 to 12 months, and faster with daily sunscreen and ingredients that have trial evidence, such as azelaic acid and topical retinoids. Hydroquinone is the classic treatment, but in the US it’s no longer legal to sell over the counter. The single most important step is preventing new marks by treating acne early and protecting skin from light.

What is post-inflammatory hyperpigmentation?

PIH is extra pigment left behind after skin inflammation. StatPearls explains that inflammatory chemicals released during a breakout stimulate pigment cells (melanocytes) to overproduce melanin. Some of that pigment stays in the top layer of skin; some can drop into the deeper layer, where immune cells hold on to it.

It is far more common in darker skin. StatPearls notes it is more common and more severe in Fitzpatrick skin types III to VI, occurs equally in men and women, and can affect as many as 65% of people with darker skin tones who have acne.

PIH is flat. If the skin is dented or raised, you’re looking at a scar instead (see acne scars vs dark spots).

How long does PIH last?

It depends on how deep the pigment sits:

• Epidermal (shallow) PIH looks tan to dark brown. StatPearls says it improves readily, typically within 6 to 12 months. The AAD agrees that a spot a few shades darker than your natural skin usually fades within 6 to 12 months.
• Dermal (deep) PIH looks blue-grey. It improves slowly and may be permanent; the AAD notes deeper discoloration can take years.

StatPearls stresses that fading “can take months to years,” that combination treatment tends to work better than a single product, and that marks commonly come back without good sun protection. Overly aggressive treatment can make PIH worse, so gentle and consistent beats harsh and fast.

PIH vs PIE: what’s the difference between brown and red marks?

Red, pink or purple marks are a different thing called post-inflammatory erythema (PIE). A 2013 report in the Journal of Clinical and Aesthetic Dermatology describes PIE as leftover redness after inflammatory acne, seen mostly in lighter skin types (I to III), whereas PIH is a pigment change more typical of darker skin. Both tend to fade over time, and some people have both.

The distinction matters because treatments differ. Treatments aimed at pigment, such as hydroquinone, are designed for PIH rather than redness. PIE has less research behind it: a 2024 placebo-controlled trial found 15% azelaic acid gel reduced both PIE and PIH, and the 2013 report describes pulsed dye laser for stubborn red marks based on case examples.

Does sunscreen really help dark marks fade?

Yes, and it’s the foundation everything else rests on. StatPearls lists daily broad-spectrum sunscreen first among PIH treatments and warns recurrences are common without it. The AAD recommends SPF 30 or higher, broad-spectrum, water-resistant and non-comedogenic, reapplied every two hours outdoors, and specifically a tinted sunscreen containing iron oxides, because iron oxide also blocks visible light, which can trigger dark spots in darker skin.

There’s some direct evidence for the tint. A 2020 study in people with skin type IV found iron oxide-containing tinted formulations significantly protected against visible light-induced pigmentation compared with untreated skin or an untinted mineral SPF 50+ sunscreen. More on choosing one in moisturizer and sunscreen for acne.

Which ingredients have evidence for PIH?

Azelaic acid

Azelaic acid is appealing because it treats acne and dark marks at once. In a 2024 randomised, double-blind, placebo-controlled trial (72 people enrolled, 60 completed), 15% azelaic acid gel reduced both PIE and PIH over 12 weeks compared with placebo. About two-thirds of the azelaic acid group had mild redness, tingling, dryness, itching or peeling that settled within about a week. An earlier 16-week pilot study of 20 adults with acne and moderate to severe PIH also reported improvement in both, though it had no control group. The AAD says azelaic acid is thought to be safe in pregnancy. More in azelaic acid for acne.

Topical retinoids

Retinoids speed skin turnover and treat the acne causing new marks. A 2022 review of retinoids in skin of colour summarises the key trials: a 40-week vehicle-controlled study of tretinoin 0.1% cream in 68 Black participants showed improvement as early as week 4, but half of those treated had skin reactions; an 18-week trial of tazarotene 0.1% cream in 74 people with skin types III to VI significantly reduced acne-related PIH versus vehicle. The review’s key warning is that retinoid irritation can itself worsen hyperpigmentation, which is why lower-strength, gentler formulas and slow introduction matter (see how to start adapalene). The AAD says most experts recommend stopping tretinoin and adapalene in pregnancy, and tazarotene can cause birth defects.

Hydroquinone

StatPearls calls hydroquinone the “mainstay of treatment” for PIH. But its US status has changed. The FDA says that since the CARES Act took effect in September 2020, there are no legally marketed over-the-counter skin lightening products, and OTC products containing hydroquinone are considered unapproved new drugs and misbranded. In its 2022 warning, the FDA named a prescription triple-combination cream (hydroquinone 4%, tretinoin 0.05% and fluocinolone acetonide 0.01%, per StatPearls) as the only FDA-approved drug containing hydroquinone, approved for short-term treatment of melasma, and said it should only be used under a licensed clinician’s supervision. The FDA has received reports of rashes, facial swelling and ochronosis, a bluish-black skin discoloration. The AAD notes dermatologists can prescribe hydroquinone and warns against imported lightening products that may secretly contain steroids or mercury. So hydroquinone is a conversation with a clinician, not a shopping-cart item.

Niacinamide

Niacinamide is gentle and popular, but the evidence for acne marks is thin. The best-known study, a 2002 paper in the British Journal of Dermatology, found a 5% niacinamide moisturiser reduced hyperpigmentation compared with vehicle over 4 weeks in 18 people, and in lab tests it blocked the transfer of pigment to skin cells by 35–68%. That’s a small study in general hyperpigmentation, not acne PIH specifically. Reasonable as a low-risk addition, but not a proven fix (see niacinamide for acne).

The AAD also lists glycolic acid, kojic acid and vitamin C among ingredients to look for.

Do chemical peels or lasers help PIH?

Sometimes, but they are double-edged. StatPearls lists glycolic, salicylic and TCA peels, plus certain lasers, as options for persistent PIH, while warning both “can cause skin irritation and additional hyperpigmentation.” A 2018 review notes dermatologists often use lightening agents before and after peels, and that deep peels should be avoided in skin types IV to VI. These belong in the hands of a clinician experienced with darker skin; see chemical peels for acne.

How can you prevent new dark marks?

• Treat acne early and consistently. Fewer inflamed spots means fewer marks; the AAD advises treating the underlying skin condition.
• Don’t pick or squeeze. The AAD links picking to more scarring (see should you pop pimples?).
• Use tinted sunscreen daily, plus a hat and shade at midday.
• Go gentle. The AAD recommends gentle skin care products, and StatPearls warns overly aggressive treatment can worsen PIH.

For a step-by-step routine, see how to fade acne marks.

Frequently asked questions