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What you need to know Acne Scarring (PIH)

What Is Post-Inflammatory Hyperpigmentation?

Post-inflammatory hyperpigmentation, or PIH, is the medical term used to describe discoloration of the skin that follows an inflammatory wound. It is the skin's natural response to inflammation.1

PIH usually looks like a flat area of discoloration on the skin. It can range in color from white, pink to red, purple, brown, or black, depending on your skin tone and depth of the discoloration.

PIH develops when a wound or irritation, like a scrape, rash, or pimple, causes the skin to become inflamed. As the skin heals, it produces too much melanin. Melanin is the protein in the skin that gives the skin its color. It's the excess melanin that darkens and discolors the skin.1 This discoloration remains even after the wound has completely healed.

It can develop in all skin types, but it tends to be more severe and longer-lasting for people with medium to dark complexions. PIH affects both men and women equally.

Acne Is a Cause

PIH is very common. Most people with acne have some degree of it. And it's not just the big blemishes that cause these spots: Hyperpigmentation can follow even relatively minor pimples and papules. That said, the more inflamed a breakout, the larger and darker the PIH spot tends to be. Picking or popping a pimple increases the chance of developing PIH, simply because you're increasing inflammation.

There are other causes of PIH, including sunburn, chemical peels, dermabrasion, laser resurfacing.

Acne Scars vs. Post-Inflammatory Hyperpigmentation

You may be relieved to learn that PIH is not true scarring. It is often called "pseudo scarring" because although it leaves a mark on the skin for a period of time, it does not actually damage the follicle.

True acne scars occur when there is either a loss of tissue, causing a pitted or depressed area, or an overgrowth of tissue leaving a raised scar.2

PIH, on the other hand, is flat. It's not pitted or raised, simply darker than the surrounding skin. This discoloration can range in color from pink to red, purple, brown, or black.

Fading Over Time

The good news is that PIH can fade away over time, even without treatment. But time is the operative word here. It can take three to 24 months for PIH to fully fade,3 although in some cases it may take longer.

The length of time it takes for PIH to fade depends on how dark the spot is compared to the surrounding skin. The bigger the contrast between the macule and your natural skin tone, the longer it will take to fade.

PIH doesn't always fade away on its own. In some cases, it's more or less permanent.

There are treatments that will help. Some may not completely erase dark marks, but will at least lighten them considerably. Treatment can also help speed up fade time if you're not keen to wait for spots to lighten naturally.

Treatment Options

Over-the-counter products can be helpful in fading more subtle marks. For deeper marks or those that have been around for a long time, a prescription cream is a better choice. Your skin care doctor has a bevy of products that can do the trick.

Another good point to remember—if you beat acne you'll also stop developing hyperpigmentation. This is an important step in clearing up PIH, and another step with which your skin care doctor can help.

Whatever treatment option you choose, understand that improvement will take time.

Alpha Hydroxy Acids (AHAs)

Alpha hydroxy acids, especially glycolic acid, are a good starting point for treatment.4 Alpha hydroxy acids (AHAs) help speed up the skin's natural exfoliation process, which can help improve the look of PIH.

You can find these ingredients in a plethora of OTC "brightening" treatments. Leave-on treatments like lotions, creams, and gels will give you better results than wash-off products like cleansers.

Other OTC ingredients that can be helpful in fading hyperpigmentation are N-acetyl glucosamine, niacinamide, and vitamins A and C.5

Stronger AHA treatments are available with a prescription. AHAs are often used as anti-aging treatments too and will leave your skin soft and smooth.


Hydroquinone is a widely used treatment for PIH.6 It's available over the counter in 1 percent to 2 percent strengths, and in 3 percent to 4 percent prescription creams. Hydroquinone works by blocking the enzyme responsible for melanin production, thereby lightening the skin.

Hydroquinone creams often contain additional lightening ingredients, such as kojic acid, glycolic acid, tretinoin and other retinoids, or vitamin C. These combination creams can give you better results than using hydroquinone alone.1

Hydroquinone creams should be carefully applied to darkened areas only, to prevent the unwanted lightening of your natural skin color. Hydroquinone may cause skin irritation for some people so it's worth talking to your doctor before beginning hydroquinone treatment.

Topical Retinoids

Topical retinoids are often prescribed to treat acne.7 Retinoids help clear acne by speeding up cell turnover rates. This rapid exfoliation can also help fade PIH.

Retinoid creams include Retin-A (tretinoin) and Retin-A Micro, Tazorac (tazarotene), and Differin (adapalene). The fact that they lessen post-inflammatory hyperpigmentation as they treat acne breakouts is an added benefit.1

With the exception of Differin, these medications are available by prescription only. Obvious results may not be apparent for several weeks to several months after beginning treatment.

Be on the lookout for excessive dryness, redness, and irritation. This can trigger PIH on its own.

Azelaic Acid

Azelaic acid is another medication used to treat acne as well as PIH.1 It works by decreasing inflammation and speeding up cell turnover rates. Azelaic acid is sometimes used in conjunction with glycolic acid or tretinoin.

Some studies have shown azelaic acid to be as effective as hydroquinone at treating hyperpigmentation.8 It is a good alternative for those who may be unable to use hydroquinone.

Azelaic acid is available by prescription only. As always, monitor your skin for redness and irritation and let your doctor know right away if you experience these side effects.

Salon and In-Office Treatments

More persistent cases of PIH can be treated professionally at skin spas, medi-spas, or your dermatologist's office. Treatments include various chemical peels1 and/or microdermabrasion.

But just one treatment isn't enough to fade hyperpigmentation. You'll likely need a series of treatments spaced a week or so apart (depending on the procedure you're having done).

Treatment Tips

Before you jump in and start treating your PIH, use these tips to set the stage for the best results possible.

  • Your acne should be under control or at least being treated. Otherwise, each new pimple could cause another dark spot and you would never get ahead of the curve (and never see the clear, even skin tone you're looking for). Over-the-counter acne products are effective for treating mild acne.9 More stubborn or severe breakouts need to be treated with prescription acne medications if you want to see real improvement.

  • Use sunscreen every day. The sun may darken the discolorations1 and increase fading time. Plus, many PIH treatments (and many acne treatments, too) can make your skin more sensitive to the sun. If you're worried that sunscreen could make your breakouts worse, don't be. There are many sunscreens available that are appropriate for breakout-prone skin.

  • Monitor your skin for irritation. Although they are helping you clear your skin, acne treatments and PIH treatments alike also have the potential for causing irritation.1 Unfortunately, irritated skin could lead to even more dark spots and uneven skin tone. If PIH is a problem for you, let your doctor know if your skin becomes irritated from your acne treatments.

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