PIE vs. PIH: What’s the difference and why won’t your acne marks go away?
An acronym I’ve said a lot in my treatment room is PIH or PIE and I always get asked “What does that mean?”. So let’s talk about these skin conditions; what they are, what they look like, and how to treat them.
One of the most common misconceptions I hear is that these leftover marks are acne scars. In many cases they aren’t actually scars at all. They may be post inflammatory hyperpigmentation (PIH) or post inflammatory erythema (PIE). While they can look similar, PIH and PIE are caused by different processes in the skin which means understanding what you’re dealing with is important when deciding how to treat it.
What is PIH?
Post inflammatory hyperpigmentation (PIH) is excess pigment that develops after inflammation or injury to the skin, including acne. PIH typically appears as brown, tan, or darker colored spots where a breakout used to be. And when the skin experiences inflammation, it can trigger excess melanin production which leaves pigment behind even after the blemish itself has healed. PIH can happen to anyone, but it tends to be more noticeable and persistent in deeper skin tones.
What is PIE?
Post inflammatory erythema (PIE) typically appears as pink, red, or purplish marks after a breakout. Unlike PIH, PIE isn't primarily caused by excess melanin. The redness is related to changes in the small blood vessels near the surface of the skin following inflammation. If your acne is gone but you're left with stubborn red or pink spots you may be dealing with PIE rather than pigmentation.
How to spot the difference
The easiest way to spot the difference between these two is by their color. Post inflammatory hyperpigmentation (PIH) will show as tan, brown, gray sometimes even black marks on the skin. While post inflammatory erythema (PIE) will show as pink, red, or purplish marks. And yes, you can have both at the same time especially if you have experienced inflamed acne lesions before.
Why are they taking so long to fade?
Unfortunately, neither PIH nor PIE disappears overnight.
Repeated inflammation, picking at breakouts, sun exposure, irritation and using overly aggressive skincare can all make post acne marks appear more noticeable or take longer to improve. This is also why throwing every brightening acid or exfoliant you can find at your skin isn't necessarily the answer either. Over treating your skin can create additional irritation and inflammation which is the exact opposite of what we're trying to accomplish.
What actually helps - Ingredients to look for to treat PIH
If your post-acne marks are brown or darker than your natural skin tone, look for ingredients that help brighten uneven pigmentation and encourage healthy skin cell turnover. Some of my favorites include:
Mandelic Acid - One of my favorite ingredients for acne prone skin. This AHA (alpha hydroxy acid) gently exfoliates while helping improve the appearance of breakouts, uneven texture, and post inflammatory pigmentation.
Azelaic Acid - A great multitasking ingredient for acne prone skin that can help improve the appearance of uneven pigmentation while also calming visible redness.
Vitamin C - An antioxidant that helps brighten the appearance of the skin, support a more even looking complexion, and provide additional antioxidant protection.
Retinoids - Helps to increase skin cell turnover and can gradually improve uneven tone, texture, and post acne marks. They should be introduced slowly, especially if your skin is sensitive or already using other active ingredients. Refer to a professional to find the right product for you.
Niacinamide - Supports the skin barrier while helping improve the appearance of uneven tone and overall skin health.
What actually helps - Ingredients to look for to treat PIE
If your marks are primarily red, pink, or purplish the goal isn't simply to “brighten” them. PIE is associated with lingering vascular changes after inflammation so keeping the skin calm and minimizing additional irritation is especially important. Look for ingredients such as:
Azelaic Acid - One of the most useful ingredients when redness and acne are both concerns. It can help calm the appearance of inflammation while also addressing uneven pigmentation.
Green Tea - An antioxidant rich ingredient that can help soothe the appearance of redness and support skin exposed to environmental stressors.
Barrier supporting ingredients - Ingredients such as ceramides can help strengthen and support the skin barrier, which is especially important when the skin is irritated or recovering from acne.
The most important ingredient - SPF
You can have the most carefully planned skincare routine in the world, but daily sunscreen is essential especially when you're trying to improve post acne marks. UV exposure can worsen pigmentation and make PIH/PIE more persistent. Visible light can also contribute to hyperpigmentation particularly in deeper skin tones. A broad spectrum sunscreen worn consistently helps protect your skin while you're working on improving existing discoloration.
And remember: more active ingredients doesn't mean faster results. Using multiple acids, scrubs, retinoids and brightening products at the same time can irritate your skin and potentially create even more inflammation. The best routine is one that's appropriate for your skin and that you can use consistently.
Not sure what you’re dealing with?
This is one of the biggest things I want my acne clients to understand. If you're still experiencing frequent breakouts, we need to address the active acne while working on the marks it leaves behind. Otherwise, we're constantly trying to correct old marks while new ones continue appearing. Clear the acne. Support the skin. Then continue working on the discoloration and redness.
You don't have to figure it out on your own.
At Esthetics by Katelyn, treatments are customized based on your skin, concerns, and goals rather than taking a one size fits all approach. Whether you're struggling with active acne, stubborn post breakout marks, or simply aren't sure what your skin needs we can create a plan that makes sense for you.