Post-Inflammatory Hyperpigmentation (PIH)

Post-inflammatory hyperpigmentation, or PIH, is the flat, darkened patch of skin that can be left behind after inflammation or injury heals. It commonly follows acne breakouts, but can also appear after eczema, cuts, burns, or irritation from aggressive skincare.

PIH occurs because inflammation stimulates pigment-producing cells to make extra melanin, which is deposited in the skin as it heals. It appears as tan, brown or, in deeper skin, greyish or darker marks, and is generally more noticeable and longer-lasting in richer skin tones. Importantly, PIH is a pigment change in already-healed skin, not an open lesion; it is also distinct from post-inflammatory erythema, which is red rather than brown.

PIH often fades on its own, but this can take many months, and the process is slow. General directions discussed for supporting fading include consistent daily broad-spectrum sun protection, since sun exposure deepens and prolongs marks, along with ingredients that act on the pigment pathway or promote even turnover, such as niacinamide, azelaic acid, tranexamic acid and gentle exfoliating acids. Avoiding further irritation and picking is also important, since new inflammation can create new marks.

This is general educational information, not medical advice. Because pigmentation can be complex and easily worsened by the wrong approach, persistent, widespread or uncertain cases warrant assessment by a dermatologist.