When a pimple goes away, why does it take so long for that lingering pinkish-red spot to fade? This phenomenon is technically called post-inflammatory erythema. And if you’ve never heard of it, that’s because the term was only coined ten years ago, to distinguish pink, red or purple post-acne lesions from other types of post-breakout dark marks.

With the help of dermatologist Sandra Lee, MD (aka Dr. Pimple Popper), we’re answering all of your questions: what causes those red spots to form in the first place, why some of them turn brown, and most importantly, what you can do to treat and prevent post-inflammatory erythema. 

4 minute read 

What is post-inflammatory erythema?

Also known as PIE, these are the pink, red, or sometimes purple marks that show up as a wound is healing. In cases of inflammatory breakouts (like papules, pustules and cysts), PIE is sometimes referred to as post-acne erythema.

You can think of pimples as mini-wounds. When your immune system springs into action to fight off acne-causing bacteria, inflammation results. As the skin begins to heal, tiny blood vessels (aka capillaries) can dilate and become damaged — resulting in that telltale redness. 

Even though post-inflammatory erythema can linger for months (or years), its temporary nature sets it apart from true acne scarring.

Why do some people get post-acne erythema?

Not everyone who has acne will develop PIE, and the severity can vary from person to person — even from pimple to pimple. That’s because post-inflammatory erythema is dependent on inflammation: so if you have non-inflammatory acne (blackheads and whiteheads), you’re not likely to develop pink or red marks. But if your breakouts include inflammatory papules, pustules, nodules or cysts, chances are you’ll see some of that redness as they heal.

People with fair skin — Fitzpatrick types I, II and III — tend to be more susceptible to post-acne erythema. The same holds true for those with thinner skin, since healing skin tends to be even thinner to begin with. This makes blood vessels become even more apparent during the skin repair process.

What’s the difference between PIE and PIH?

So here’s how post-inflammatory erythema differs from post-inflammatory hyperpigmentation:

• Color: PIE is pink to red, while PIH can be tan, brown, or grayish looking.
• Cause: PIE involves blood vessels, whereas PIH results from excess melanin deposited during healing.
• Incidence: Generally speaking, fair-skinned people are more likely to experience PIE, whereas darker-skinned types are more likely to get PIH.

Dr. Pimple Popper tip: try SLMD Dark Spot Fix if you're looking to fade the look of post-inflammatory hyperpigmentation.

How do you avoid post-inflammatory erythema?

According to Dr. Lee, the best way to handle post-inflammatory erythema is to minimize the inflammation that causes it. Here are her top tips for avoiding PIE:

• Treat your acne. Getting your acne under control means that you’re less likely to wind up with breakout-induced inflammation in the first place. Try: SLMD Acne System or Sensitive Skin Acne System, BP Spot Treatment.
• Avoid popping your pimples. Picking and squeezing are off-limits, too, as anything that might make the wound worse can also make PIE worse. Try: SLMD Spot Check acne patches.
• Be gentle with your skin. Scrubbing or over-exfoliating can exacerbate irritation and inflammation, making red marks worse.

Don't pick your pimples! Try medicated SLMD spot treatments instead.

What’s the best way to treat post-acne erythema?

In many cases, notes Dr. Lee, PIE heals on its own over time. If you want to speed the process, there are a few methods you can try:

• Spot treat with salicylic acid. This beta hydroxy acid can help reduce inflammation and clear out pore-clogging debris, speeding healing. Try: SLMD Salicylic Acid Spot Treatment.
• Try topical retinoids. Tretinoin and its over-the-counter cousin, retinol, helps quell inflammation and increase cell turnover, which can reduce red marks. Try: SLMD Retinol Serum.
• Incorporate antioxidants. Ingredients that neutralize free radicals, like vitamin E, niacinamide and vitamin C, help calm down irritated skin. Try: SLMD All Bright toner, Bright Future Vitamin C Serum.
• Wear sunscreen — always. This one’s a no-brainer, since we all know that UV exposure results in red skin, which is exactly what we’re trying to avoid with PIE. Try: SLMD Dual Defender SPF 30.
• Book a laser treatment. Your dermatologist can determine if you’re a candidate for an in-office procedure like IPL or PDL to target the redness.