What Is Post-Inflammatory Hyperpigmentation (PIH)?

Post-inflammatory hyperpigmentation
Post-inflammatory hyperpigmentation. Photo (c) A.D.A.M.

Your acne is clearing up and your skin is looking better every day. But then you notice dark discolorations everywhere the acne lesions have healed. Is it acne scarring?

What are those darks marks on my skin?

Those dark spots are called post-inflammatory hyperpigmentation (sometimes abbreviated PIH).  It's the medical term given to discoloration of the skin that follows an inflammatory wound.

Post-inflammatory hyperpigmentation looks like flat areas of dark discolorations on the skin.

  It can happen anywhere on the face and body.

They can range in color depending on your skin tone and depth of the discoloration.  If you're fair-complected, your post-inflammatory hyperpigmentation spots are probably going to be pink to red, or purple colored.  Darker complexions will notice PIH spots are brown to black. 

PIH spots can be a range of colors, however, the skin will not be pitted or depressed. It looks more like a discolored freckle on the skin, or even a larger, splotchy discoloration of the skin.  Early on, these spots may look shiny, or like "new skin."

Why do pimples leave these discolored spots?

Let's break down the term post-inflammatory hyperpigmentation.  The prefix post- means "after."  Inflammatory is fairly self-explanatory, anything that causes inflammation -- redness, swelling, and pain.  Sounds like a typical pimple, right?  

Hyper- means "over" or "excessive."  Pigmentation refers to the color of the skin.

  So, altogether, postinflammatory hyperpigmentation literally means "excessive color after inflammation."

While the skin repairs itself as a pimple heals, it can make too much melanin (the substance that gives your skin its color).  The result is spot that is darker than the surrounding skin.  It is the skin's natural response to inflammation.

And it's not just pimples that cause post-inflammatory hyperpigmentation.  Any injury, wound or irritation can cause post-inflammatory hyperpigmentation to develop -- cuts and scrapes, burns, rashes and, yes, acne.

Take heart in the knowledge that, while incredibly annoying, these dark spots are completely normal.  Nearly every person with acne will develop post-inflammatory hyperpigmentation to some degree.

PIH affects both men and women equally, but it is more common (and longer lasting) in darker skin tones. It affects both men and women equally.  Post-inflammatory hyperpigmentation is not a true scar, and it isn't always permanent.

Post-inflammatory hyperpigmentation is completely a cosmetic problem.  But post-inflammatory hyperpigmentation is annoying; some people find it more bothersome that actual pimples.  PIH often fades, all on its own, over time.  There are also plenty of treatment options available that can help fade those pesky dark spots faster.

Next steps:

What Causes Post-Inflammatory Hyperpigmentation?

How To Treat Post-Inflammatory Hyperpigmentation


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