Post Inflammatory hyperpigmentation, or PIH, is the medical term given to discoloration of the skin that follows an inflammatory wound. It is the skin's natural response to inflammation. PIH presents itself as a flat area of discoloration on the skin (macule) ranging from pink to red, purple, brown or black, depending on your skin tone and depth of the discoloration.
PIH develops when a wound, rash, pimple, or other stimuli causes skin inflammation, which triggers the skin to produce too much melanin.
A post inflammatory hyperpigmentation macule often is the remnant of an inflamed acne lesion. PIH macules can follow relatively minor pimples and papules, in addition to more serious lesions. However, the more inflamed a breakout, the larger and darker the PIH macule tends to be. Picking or popping a pimple increases the chance of developing post inflammatory hyperpigmentation.
You can identify post inflammatory hyperpigmentation by carefully examining the skin. PIH macules can be a range of colors, however, the skin will not be pitted or depressed. It may look like a discolored freckle on the skin, or it may present as a larger, dark discoloration of the skin.