Why does post-inflammatory hyperpigmentation cause dark patches on skin?

Inflammation signals pigment-producing cells to become more active. They release extra melanin, the substance that gives skin its colour. As the original spot, rash, bite, burn, or blemish calms, that extra pigment can remain in the affected area, creating a brown, grey, or deeper-looking patch. Pigment closer to the surface may look brown, while pigment deeper in the skin can appear grey-brown and may take longer to fade.

The mark follows the area that was inflamed, so it may have the shape or outline of the earlier problem. Sun exposure can make the contrast more noticeable. Post-inflammatory hyperpigmentation can occur in any skin tone, and irritation from picking or harsh products may prolong the colour change.

Use gentle, fragrance-free cleansing and moisturising, and avoid scratching, squeezing, or repeatedly rubbing the area. Daily broad-spectrum sunscreen on exposed skin helps limit additional darkening; reapply as directed on the product label, especially during outdoor time. Do not start strong lightening products or exfoliating acids on irritated skin without professional guidance, because more inflammation can deepen the patch.

A clinician can check whether the colour fits post-inflammatory hyperpigmentation and discuss options suited to your skin and the original trigger. Improvement is gradual rather than immediate, particularly when pigment sits deeper in the skin.

Arrange a skin assessment if a patch keeps enlarging, changes in several ways, bleeds, crusts, becomes painful, or has no clear connection with a previous rash or injury. Seek prompt care for rapidly spreading redness, warmth, swelling, pus, or fever. A changing dark mark needs examination because not every pigmented patch is post-inflammatory hyperpigmentation.

Ask what caused the original inflammation, whether the colour is superficial or deeper, which products are least likely to irritate your skin, and how long a reasonable trial of a treatment should last.