This week, let’s take a deep look at the albatross hanging around the neck of many skincare addicts: long-term discoloration caused by acne.
There are three types of long-term physical changes caused by an acne lesion: postinflammatory hyperpigmentation (PIH), postinflammatory erythema (PIE), and acne scars. Acne scars have a different texture than the surrounding skin, and are either raised or lowered. I won't be addressing acne scars in this post; they are best treated by a dermatologist.
Postinflammatory Hyperpigmentation (PIH)
PIH appears after inflammation – in our case, after a pimple heals – and is caused by a deposit of excess melanin. Scientists aren’t 100% sure why this happens, but it’s likely that the skin’s inflammation response triggers melanogenesis, or the process of creating new melanin.
(Melanin is the pigment whose concentration determines our skin tone. Caucasian people have less melanin, while people of African descent have way more.)
Because melanin is brown or black, postinflammatory hyperpigmentation will appear somewhere between tan/light brown to almost black. PIH is much more likely to affect people of color, since their skin has more melanin to begin with. It’s been studied in depth, and there are a lot of great treatment options, although PIH will normally fade on its own within 6-12 months.
Postinflammatory Erythema (PIE)
This is a brand new term (seriously, it was coined in 2013
) to describe pink or red spots
that linger after an acne lesion heals. PIE consists of “discrete erythematous macules”
– that is, little spots of redness caused by damage or dilation of capillaries under the skin.
Because it’s such a new concept, there’s not much in the way of treatment. The only thing I could find was pulsed dye laser treatment, which a dermatologist would do for you. Fortunately, like PIH, PIE will fade on its own over time.
The Difference Between PIH and PIE
PIH will fall on the color scale from tan to dark brown, and is more likely to affect people of color. PIE is pink or red, and is more likely to affect light-skinned folks. All the treatment options for PIH focus on inhibiting or destroying melanin, which makes sense for a condition caused by an excess of melanin (PIH). Unfortunately, melanin plays a 0% role in PIE, so none of that is gonna help.
There are a few ways to fade PIH. The first and MOST IMPORTANT is sunscreen. PIH is caused by excess melanin production. Guess what else causes melanin production? (It's the sun.)
Melanin absorbs UV radiation from the sun and can protect your skin from UV damage. (That’s why people of color, who have more melanin, get fewer sunburns.) When your skin gets sun damage, your body assumes that’s just how it is now, that you’ll always be pelted with UV radiation, so it creates more melanin to compensate and protect your skin. (That’s why you get darker when you tan.)
This can make PIH exponentially worse – if you’re trying to heal PIH, you don’t want to do anything that will make even more melanin. Wear sunscreen every day, especially if you’re trying to fade PIH. It doesn’t matter if you don’t burn, you still need to wear sunscreen.
Another common mechanism has to do with tyrosinase, an enzyme that facilitates melanin production. Many PIH-fighting ingredients work by inhibiting tyrosinase, so your skin can’t produce as much new melanin.
Common Tyrosinase Inhibitors
In studies of PIH-lightening abilities, kojic acid is the standard that everything is measured against. It’s extremely effective, but potentially very irritating, and should be used in concentrations of 1-4%. Kojic acid is powerful stuff. Ask your dermatologist if you want to start using it.
A safer derivative of hydroquinone, arbutin has the same tyrosinase-inhibiting effects without causing cell death. Unlike most of the ingredients listed here, arbutin is actually much more effective on light skin tones than on dark ones. One thing to be wary of: in too high doses, arbutin can actually cause postinflammatory hyperpigmentation.
Another super-great tyrosinase inhibitor, azelaic acid also kills off abnormal melanocytes. It generally causes less irritation and fewer side effects than similarly powerful ingredients like hydroquinone and retinoids.
Licorice Root Extract
This is an ingredient that has been used in traditional skin care for thousands of years, and has a scientifically-proven ability to inhibit tyrosinase. It’s a great, gentle way to lighten PIH and brighten your overall skin tone.
This much-loved ingredient is also a tyrosinase inhibitor. All forms of vitamin C (including L-Ascorbic Acid and Magnesium/Sodium Ascorbyl Phosphate) will fade PIH. L-Ascorbic Acid is also an exfoliant and antioxidant, while MAP/SAP are much more stable and less likely to cause irritation.
Rounding out our list of tyrosinase inhibitors is NAG. This ingredient is best used at concentrations of 2% and works synergistically with niacinamide to make both ingredients work better.
Other ingredients to treat PIH
There are a number of other mechanisms to fade PIH besides inhibiting tyrosinase. Here are some of those players.
God, what can’t retinoids do? PIH-wise, they cause increased cell turnover, meaning you’re getting rid of the abnormal melanocytes faster. Plus, retinoids can have anti-inflammatory effects, which can help prevent future postinflammatory hyperpigmentation. Tretinoin is the best retinoid for PIH, but it can be very irritating, so start with a low percentage and work your way up.
Alpha-hydroxy acids also increase cell turnover, plus they disperse melanin in the basal layer of the epidermis.
Niacinamide, in addition to its many magical qualities, interrupts the transfer of melanin between skin cells. It might also decrease melanogenesis, or the production of melanin. It’s best in concentrations of 2-5% and is one of my all-time favorite ingredients – and one of the most thoroughly scientifically studied and reviewed cosmetic ingredients. Combine it with N-acetyl glucosamine to kick both ingredients into the stratosphere.
I think I have PIE, not PIH. What do I do?
Wait for more research to come out, I guess. Like I mentioned above, one study indicated pulsed dye laser treatment was effective at treating PIE. Unfortunately, none of the ingredients listed in this post will do anything for PIE, since all these ingredients affect melanin, and PIE is melanin-free. It will fade on its own over time, but there’s not much we know in terms of treatment.
Your best bet is to avoid PIE in the first place, by both treating your acne so you get as few lesions as possible, and reducing inflammation so the subsequent PIE isn’t as bad. Try using tretinoin or a BHA, both of which fight acne and reduce inflammation. DON’T PICK! Picking, squeezing, or otherwise being rough with your acne will trigger a bigger inflammatory response, which will make the subsequent PIE worse. Other than that, concealer is your friend.