PIE (Post-Inflammatory Erythema)
Definition
Post-inflammatory erythema (PIE) refers to the flat, pink to red or purple marks left on the skin after an inflammatory wound — most commonly acne — has healed. Unlike post-inflammatory hyperpigmentation (PIH), which involves excess melanin and appears as brown marks, PIE is caused by damaged or dilated blood vessels and capillaries beneath the skin's surface. PIE is more common in lighter skin tones and can be distinguished from PIH by pressing a glass slide against the mark — PIE will temporarily fade under pressure while PIH will not. PIE can take months to years to fade on its own as the blood vessels heal. Treatment options include azelaic acid, niacinamide, centella asiatica, and diligent sun protection. Professional treatments like pulsed dye laser, vascular lasers, and microneedling can also accelerate healing. Preventing PIE starts with not picking at acne and managing inflammation early.
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