Post-Inflammatory Hyperpigmentation
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Direct answer
Post-inflammatory hyperpigmentation is excess melanin deposited in the skin after inflammation, injury or treatment. It is most common and most persistent in darker skin types, where pigment lies in the epidermis or within dermal melanophages that hold it for months or longer. Management combines strict sun protection, control of the original disease and topical depigmenting agents.
What you must remember
- Mechanism: inflammatory mediators such as prostaglandins and cytokines stimulate melanocytes, and the melanin is transferred to keratinocytes.
- Epidermal pigment: the pigment lies within keratinocytes and is accentuated by Wood's lamp, and it usually clears over months.
- Dermal pigment: melanophages in the dermis hold the pigment for longer, and Wood's lamp does not accentuate it.
- Common causes: acne, eczema, lichen planus, friction, burns, lasers and cosmetic procedures.
- Skin of colour: Fitzpatrick types IV to VI show more and longer-lasting pigmentation after inflammation.
- Sun protection: ultraviolet exposure darkens and prolongs post-inflammatory pigment, so broad-spectrum sunscreen is the first measure.
- Topical agents: azelaic acid, tretinoin, hydroquinone, kojic acid and niacinamide are used, with a short course of topical steroid for any residual inflammation.
- Procedures: superficial peels help, while aggressive peels or lasers can produce fresh hyperpigmentation in darker skin.
A graded plan for treating pigment that follows acne
A 26-year-old woman with Fitzpatrick type V skin has brown macules left behind after her acne papules resolved. Management starts with the cause and only then turns to pigment-directed treatment.
- Treat the trigger: Control the acne, eczema or lichen planus first, since fresh inflammation renews melanocyte stimulation.
- Enforce sun protection: Advise a daily broad-spectrum sunscreen and sun avoidance, because ultraviolet exposure darkens and prolongs the pigment.
- Assess the depth: Accentuation under Wood's lamp indicates epidermal pigment, which clears faster, whereas no accentuation suggests dermal pigment that clears slowly.
- Start topical agents: Azelaic acid, tretinoin or hydroquinone is chosen according to the skin type, the tolerance and the depth of the pigment.
- Add peels with caution: Superficial glycolic or salicylic peels may be used, while deep peels are avoided because they can cause fresh pigmentation.
- Reassess and counsel: Explain that dermal pigment clears slowly and that improvement often takes months, with review at planned intervals.
Where the exam tries to catch you
Post-inflammatory hyperpigmentation questions test cause before cure and the depth of the pigment.
- Trap: treating the pigment with a lightening agent while the eczema or acne continues. Correct: ongoing inflammation keeps stimulating melanocytes, so the trigger must be controlled first.
- Trap: using aggressive lasers or deep peels on dark skin to clear the pigment quickly. Correct: these can cause fresh post-inflammatory hyperpigmentation, so gentle, superficial and graded treatment is preferred.
- Trap: believing epidermal and dermal pigment respond equally well to treatment. Correct: epidermal pigment lightens faster with topical therapy, while dermal pigment persists and responds poorly.
Frequently asked questions
Why is post-inflammatory hyperpigmentation more common in darker skin?
Darker skin types, Fitzpatrick IV to VI, have more active melanocytes and larger melanosomes, so inflammation produces more visible pigment. Mediators released during inflammation stimulate these melanocytes strongly, and the resulting pigment persists longer.
How does Wood's lamp help in post-inflammatory hyperpigmentation?
Wood's lamp accentuates epidermal pigment, which appears more intense under ultraviolet light, while dermal pigment shows no change. Epidermal post-inflammatory hyperpigmentation usually responds better to topical treatment than dermal pigment does.
Which topical agents are commonly used for post-inflammatory hyperpigmentation?
Azelaic acid, tretinoin, hydroquinone, kojic acid and niacinamide are commonly used for post-inflammatory hyperpigmentation. The choice depends on the skin type, the underlying disease and the risk of irritation, and hydroquinone is used cautiously because of adverse effects such as ochronosis.
Why must lasers be used with caution in darker skin with post-inflammatory pigment?
Lasers and deep peels can injure melanocytes and trigger fresh post-inflammatory hyperpigmentation in darker skin. Conservative settings and test patches reduce this risk, and the treatment should be started only after the underlying inflammation has been controlled.