Post Inflammatory Hyperpigmentation

Post-inflammatory hyperpigmentation (PIH) is an acquired hypermelanosis following cutaneous inflammation or injury, more frequent and persistent in patients with darker skin (Fitzpatrick types III to VI).

• Common causes: acne vulgaris, atopic dermatitis, psoriasis, lichen planus, fixed drug eruption, burns, insect bites, trauma, procedures (lasers, peels), and infection.
• Mechanism: inflammatory mediators (prostaglandins, leukotrienes, cytokines) stimulate melanocytes and increase melanin production and transfer.
• Epidermal PIH (brown) resolves in months to years; dermal PIH (blue grey, melanophages) persists longer.
• Aggravated by sun exposure; has substantial psychosocial burden.

• Macules or patches of light to dark brown or blue grey pigmentation confined to the site of the preceding inflammation, with shape mirroring the original lesion.
• Asymptomatic; may follow subtle inflammation.
• Particularly prominent in acne in dark skinned patients.
• Distinct from scarring or true atrophy.

• Clinical diagnosis based on history of preceding inflammation and morphology.
• Wood lamp: epidermal pigmentation accentuated; dermal is not. Dermoscopy shows brown structureless areas or blue grey dots.
• Biopsy rarely needed: epidermal melanin increase and/or dermal melanophages with a mild infiltrate.
• Evaluate for ongoing inflammatory disease, drug eruptions (minocycline, amiodarone), and endocrine diseases (Addison disease) if diffuse.
• Exclude melasma, lentigines, tinea versicolor, naevi, and melanoma (especially if asymmetric or evolving).

• Treat and prevent the underlying inflammatory condition (e.g. acne with topical retinoids, benzoyl peroxide, and non-irritating regimens); avoid picking.
• Daily broad spectrum SPF 30 to 50+ sunscreen with iron oxide.
• Topical depigmenting agents (8 to 12 weeks): hydroquinone 2 to 4% (with tretinoin 0.025 to 0.05%, plus a mild steroid in triple combination), azelaic acid 15 to 20% (also anti-acne), tretinoin or adapalene 0.1 to 0.3%, niacinamide 4 to 5%, kojic acid, tranexamic acid topical 3 to 5%, arbutin, and vitamin C 10 to 20%.
• Procedural options for persistent pigment: superficial chemical peels (glycolic acid 30 to 50%, salicylic acid 20 to 30%, mandelic acid), low fluence Q-switched lasers or picosecond laser for dermal pigment; avoid high energy lasers that risk worsening.
• Oral tranexamic acid 250 mg twice daily in recalcitrant cases (screen for thrombosis).
• Camouflage cosmetics, patient education about slow resolution (6 to 24 months), and psychological support.