Beauty 101: PIH & PIE

If you’ve done any reading whatsoever on topics like acne, scarring, freckles or even just skincare in general, you’ve probably come across the acronyms PIH and PIE. A lot of times, when people talk about them they use the terms interchangeably, even though they’re not the same thing.

-Obligatory pie joke- Huehue

I think that most of the time this stems from not really understanding the difference. This is totally forgivable because unless you’re a major skincare enthusiast or you have a science background, there really isn’t a reason for you to dive into the nuances.

Since I fancy myself a skincare junkie enthusiast and a scientist, I’m going to give you guys a simplified crash course on the differences and why you can’t treat one the same as the other.

pih: Post-Inflammatory Hyperpigmentation

Well this already sounds technical and sciencey, huh?

Basically, post-inflammatory hyperpigmentation is what happens to your skin after your body has triggered its natural inflammatory response due to some kind of (perceived) trauma.

I say “perceived” trauma because the things that cause it aren’t things we would think of as traumatic, necessarily.


  • Acne breakouts (definitely traumatic)
  • Hormonal shifts
  • Pregnancy
  • Sun exposure
  • Natural aging

Actually, now that I’m looking at that list…all of those things could totally be traumatic. I mean, GETTING OLD?! Being outside IN THE SUN?! Just thinking about those things leaves me sobbing in a dark corner.

The telltale sign of PIH is that your spots are mostly brown or black. This is because that inflammatory response I was talking about earlier causes your melanin-producing cells to kick into overdrive.

Freckles, lentigines (sun spots, plural of the official name for them, lentigo #TheMoreYouKnow) and melasma are all examples of PIH.

pie: Post-Inflammatory Erythema

First, let me clear up the most pressing matter about this topic:

Erythema is pronounced (air-uh-THEEM-ah).

Second, you won’t find much scientific literature that uses the term PIE because it hasn’t been around that long. The first paper suggesting that post-inflammatory erythema should be added to the official dermatology lexicon wasn’t published until late 2013.

Of course, PIE was happening long before then, it’s just that there was no single, unifying term that doctors and dermatologists used to describe it. This is probably also why there’s so much confusion surrounding the two.

PIE deals with reddish or purplish discolorations left on your skin from some kind of major skin trauma. This is a little different than PIH trauma because the things that cause PIE are generally pretty traumatic by any standards.


  • Cysts/acne cysts
  • Popping pimples
  • Cuts and abrasions
  • Sunburn
  • Chemical burns
  • Inflamed acne lesions (aka really crappy and painful pimples)

The Quick & Easy Test

On some skin, it can be hard to tell what’s hyperpigmentation and what’s erythema. (This is especially true for darker or olive skin tones!) Since they require different treatment, it’s important to know what you’re dealing with.

There’s a quick test you can perform that will let you know whether you’re dealing with erythema or not. If it’s a fairly large spot, just gently press on it with your fingertip and let go. You can do this test with a clear glass or something similar instead of your finger if you can’t tell just by poking.

If it temporarily disappears, it’s erythema. This effect is called blanching. If nothing changes, it’s hyperpigmentation.

So How Do I Get Rid of PIH & PIE?

If you have PIH, getting rid of it is pretty straightforward, but it does take a lot of time, consistency and PATIENCE. Almost every time someone complains to me that the process isn’t working, it’s because they either aren’t being consistent with all of the products or they haven’t given the process enough time to work.

Since PIH is a pigmentation issue, the best way to treat it is with products that inhibit melanin production and even out skin tone. Look for ingredients like niacinamide, arbutin, licorice, adenosine and bird’s nest (sometimes listed as swiftlet’s nest or swiftlet’s nest extract).

IMPORTANT NOTE – These are not bleaching ingredients! Inhibiting melanin does not mean that it will make you “whiter.” It will only help your skin return to its natural, pre-damaged tone, whatever that may be. I’m never an advocate of trying to unnaturally lighten your skin.

Unfortunately, PIE doesn’t respond to these types of products. The issues run much deeper in the skin, so topical treatments are usually ineffective. The only truly effective treatments are cosmetic lasers and, for some people, silicone sheeting. Silicone scar sheets are obviously a much cheaper and more accessible option, so I’d recommend trying that out first before you consider lasers.

Tell Me About Your Experiences!

I hope that this post helped clear up the confusion about PIH and PIE. If I’ve left any questions unanswered, feel free to ask in the comments and I’ll give you the best answer I have!

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