Post Inflammatory Redness, often called Post Inflammatory Erythema or PIE, happens when skin stays red, pink, or purplish after inflammation goes away. It shows up as flat spots of color that linger where pimples, rashes, or injuries once were.
This redness comes from changes in the tiny blood vessels right under the skin. When something irritates the skin, like acne or an allergic reaction, the body sends extra blood to fight it off. The vessels called capillaries widen to let more blood flow in. This makes the area look red while the problem is active. Even after the irritation heals and swelling fades, those capillaries can stay stretched out or damaged. They keep letting too much blood show through the skin’s surface, creating the leftover color.
Acne is the top cause of PIE. The bacteria in pimples spark a strong immune response that harms nearby vessels. The worse the breakout or the longer it lasts, the more likely you get stubborn redness. Other triggers include bug bites, eczema flares, cuts, scrapes, or even harsh scrubbing. Allergic reactions to lotions or foods can do it too. Anything that causes swelling or heat in the skin sets off the same chain: vessels dilate, blood rushes in, and some stay open afterward.
PIE differs from dark spots called Post Inflammatory Hyperpigmentation or PIH. PIH comes from extra pigment made by skin cells, turning areas brown or gray. PIE is all about blood flow, not color from melanin. It also is not scarring, which changes the skin’s texture or depth. PIE marks are flat and fade as vessels calm down over time.
The redness often feels warm and might itch a bit at first. It can last weeks to months, depending on skin type and how fast it heals. Fair skin shows it more clearly since less pigment hides the pink. Pressing on a PIE spot makes the color fade briefly because it pushes blood out of the vessels. That test helps tell it from bruises.
Sources
https://www.kins-clinic.com/blogs/post-inflammatory-erythema-from-acne-a-guide-to-causes-and-treatments
https://moawadskininstitute.com/post-inflammatory-erythema-cure/
https://www.serenityrejuvenationcenter.com/services/post-inflammatory-hyperpigmentation-pih-treatment-in-seattle/
https://massivebio.com/erythema-bio/
https://www.droracle.ai/articles/592293/what-are-the-treatment-options-for-acne-post-inflammatory-erythema
https://www.britannica.com/science/erythema
https://health.clevelandclinic.org/disney-rash
https://potozkinellis.com/facial-vein-and-redness-treatment-danville/
