Post-inflammatory hyperpigmentation is an acquired hypermelanosis that follows cutaneous inflammation or injury. It is highly prevalent in skin of color (Fitzpatrick IV–VI) and can be epidermal, dermal, or mixed. PIH significantly impacts quality of life. Management prioritizes prevention (rapid control of underlying dermatoses and irritation minimization), photoprotection including visible light, and staged depigmenting therapy. Gentle, sustained regimens are favored to avoid rebound irritation that perpetuates PIH.
Epidemiology and Risk Factors
- Common after acne, eczema, insect bites, burns, procedures (peels/lasers), and trauma.
- Higher incidence and persistence in darker skin tones.
- Exacerbated by UV/visible light exposure and ongoing inflammation or friction.
Pathophysiology
- Inflammation triggers melanocyte hyperactivity and excess melanin transfer; in dermal PIH, pigment-laden macrophages (melanophages) prolong discoloration.
- Visible light (HEVL) induces melanogenesis; iron oxides in sunscreens mitigate this.
Clinical Features and Diagnosis
- Macules/patches ranging light to dark brown at prior lesion sites; slate-gray hue suggests dermal pigment.
- Wood’s lamp may accentuate epidermal PIH; not reliable in all skin types.
- Differentiate from melasma, drug-induced pigmentation, erythema dyschromicum perstans, lichen planus pigmentosus.
Prevention and Foundational Care
- Early, effective control of primary disorders (e.g., acne, eczema).
- Strict daily broad-spectrum photoprotection SPF 50+ with iron oxide–tinted sunscreen for HEVL; hats, shade, reapplication.
- Avoid picking/scratching; minimize friction and harsh products.
Treatment
- Topical agents (first-line)
- Retinoids: tretinoin/adapalene/tazarotene to normalize turnover and enhance other agents; start slowly to limit irritation.
- Azelaic acid 15–20% (anti-inflammatory, tyrosinase modulation).
- Hydroquinone 2–4% in limited, time-bound courses (8–12 weeks) then off-cycle; consider triple combination cream in select cases.
- Non-HQ options: kojic acid, arbutin, niacinamide 4–5%, cysteamine 5% cream, tranexamic acid (topical).
- Compounded combinations (e.g., HQ + retinoid + steroid) for short induction phases, then maintenance with non-HQ.
- Systemic options
- Oral tranexamic acid (250 mg bid for 8–12 weeks) in refractory extensive PIH, especially in melasma overlap; assess thrombosis risks.
- Procedures (cautious use, experienced hands)
- Superficial chemical peels (glycolic/salicylic/lactic/Jessner) in series; pre-treat with tyrosinase inhibitors and retinoids; strict photoprotection to avoid rebound PIH.
- Low-energy fractional non-ablative lasers or microneedling as adjuncts; test spots and conservative parameters in darker skin.
- Maintenance
- Continue sunscreen and gentle skincare; maintain with azelaic acid, niacinamide, retinoids.
- Intermittent short HQ cycles for relapses; avoid continuous long-term HQ to reduce ochronosis risk.
Special Populations
- Skin of color: prioritize irritation-minimizing regimens, longer intervals between procedures, and tinted sunscreens.
- Post-procedure PIH: preconditioning, slow energy escalation, meticulous aftercare; topical steroids for a few days post-procedure may decrease inflammation.
Prognosis
- Epidermal PIH can improve within months with treatment; dermal PIH may take many months to years.
- Prevention and maintenance are key to durable results.
References (recent guidelines and key reviews)
- Consensus statements on dyschromia management in skin of color, 2022–2024.
- RCTs/meta-analyses on topical combinations and TXA, 2021–2024.
- Device-based therapy safety in darker skin, 2022–2024.
- Sunscreen strategies with iron oxides for HEVL, 2021–2024.