Post-Inflammatory Hyperpigmentation: Why Acne Marks Turn Brown — and How to Fade Them
For many people, the acne itself isn't the most frustrating part. It's the marks it leaves behind — flat, dark spots that persist for months after the breakout has cleared. These are post-inflammatory hyperpigmentation (PIH), and they're one of the most common reasons people seek prescription skincare.
What causes post-inflammatory hyperpigmentation
PIH occurs when the inflammatory process triggered by a breakout stimulates melanocytes — the pigment-producing cells in the skin — to produce excess melanin at the site of inflammation. When the inflammation resolves, the melanin remains, appearing as a flat dark mark.
PIH is not the same as a scar — it involves no structural damage to the dermis. It's a pigmentation change in the epidermis (and sometimes the upper dermis). This distinction matters because it means PIH can be treated effectively with topical actives, whereas atrophic acne scars require more intensive interventions.
Why some people get worse PIH than others:
PIH is significantly more pronounced and longer-lasting in medium to darker skin tones (Fitzpatrick types III–VI). The reason is density of melanocytes — darker skin has more melanocytes per unit area, producing a stronger pigmentation response to the same level of inflammation. What fades in weeks for lighter skin tones can persist for 12–18 months in darker skin without treatment.
This is one of the most important clinical reasons that prescription treatment for acne in darker skin tones should include PIH prevention and treatment from the outset — not just acne control.
The difference between PIH, PIE, and acne scars
PIH (post-inflammatory hyperpigmentation) — flat brown or dark marks. Melanin-based. More prominent in darker skin tones.
PIE (post-inflammatory erythema) — flat red or pink marks. Vascular, not melanin-based. More prominent in lighter skin tones. Read more about PIE and how it differs from PIH.
Acne scars — structural changes to the dermis. Atrophic (depressed) or hypertrophic (raised). Require different treatment approaches. Read about acne scar prevention.
Many patients have all three simultaneously — active PIH from recent breakouts, residual PIE from earlier lesions, and some degree of atrophic scarring from past severe inflammation.
What prescription treatment does for PIH
Prescription retinoid (tretinoin)
The Core Formula accelerates epidermal cell turnover — shedding the pigmented cells containing excess melanin faster. This is the fundamental mechanism by which tretinoin improves PIH. It also reduces the inflammatory response at the site of active lesions, preventing severe PIH from developing as acne heals.
Prescription brightening actives
The Pigment Modulation add-on targets melanin synthesis directly:
Tranexamic acid blocks the inflammatory signal that triggers melanocyte overactivation
Azelaic acid inhibits tyrosinase — the enzyme central to melanin production — and has direct anti-inflammatory properties that reduce the inflammation driving new PIH
Kojic acid provides additional tyrosinase inhibition through a complementary pathway
Hydroquinone where appropriate — the most potent prescription depigmenting agent for severe PIH
The combination of tretinoin-driven cell turnover and melanin synthesis inhibition produces faster, more complete PIH clearance than either approach alone.
Treating the acne simultaneously
PIH management in the context of active acne is incomplete if the acne isn't also being controlled — new breakouts continuously create new PIH. The Acne Modulation add-on addresses the acne driving new pigmentation while the Pigment Modulation add-on treats existing marks.
How long does PIH take to fade with prescription treatment?
Lighter skin tones (Fitzpatrick I–III): Most PIH fades significantly within 8–12 weeks of consistent prescription treatment. Older or deeper marks take longer.
Medium to darker skin tones (Fitzpatrick IV–VI): PIH is more established and longer-lasting. Meaningful improvement typically occurs at 12–16 weeks, with continued fading through 6 months. Formulation must be chosen carefully to avoid triggering new PIH through irritation — your clinician selects actives appropriate for your skin tone.
Read more about how skin tone affects melasma and pigmentation treatment and the clinical approach to different Fitzpatrick types.
Sun protection
UV exposure stimulates the same melanocyte pathways responsible for PIH — without daily SPF, treatment is fighting ongoing UV stimulation. Mineral sunscreen, SPF 30+, daily use is a prerequisite for any PIH protocol.
Getting started
The Laevo assessment covers your acne type, PIH severity, skin tone, and history. Your clinician designs a formula that addresses both the acne driving new PIH and the existing marks.
Assessment fee applies. Prescription required — not all applicants will be approved. Individual results vary. This article is for informational purposes only and does not constitute medical advice.
