While they may sound similar, PIH and PIE are different. PIH or Post-Inflammatory Hyperpigmentation represent pigmented (brown or black) spots caused by an inflammatory reaction, resulting in overproduction of melanin. A typical example is brown marks left after acne. PIE or Post-Inflammatory Erythema refers to the red / dark red marks left behind after inflammation (like acne). This happens because the capillaries near the skin surface gets damaged by the inflammation, which results in small red marks. So PIH is pigmented and looks brown / dark brown in color and PIE looks like a clogged blood inside the skin and looks red/ dark red in color.Since more research is needed on the impact of topical SA on fetures or babies, pregnant and breastfeeding, women should consult their doctor before including SA into their routine. People with specific skin conditions or health issues shall also consult their doctor before using any direct acid.