From Angela Palmer,
Your Guide to Acne.
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About.com Health's Disease and Condition content is reviewed by Casey Gallagher, MD

Your acne is clearing up and your skin is looking better every day. But then you notice dark pink or brown spots on your skin where the acne lesions have healed. Is it scarring? And what can you do about it?

What is Postinflammatory Hyperpigmentation?

Postinflammatory hyperpigmentation, or PIH, is the medical term given to discoloration of the skin that follows an inflammatory wound. It is the skin's natural response to inflammation. PIH presents itself as a flat area of discoloration on the skin (macule) ranging from pink to red, purple, brown or black, depending on your skin tone and depth of the discoloration.

PIH develops when a wound, rash, pimple, or other stimuli causes skin inflammation, which triggers the skin to produce too much melanin. Melanin is the protein in the skin that gives the skin its color. The excess melanin darkens and discolors the wounded area. This discoloration remains even after the wound or rash has healed.

PIH is very common among acne sufferers. It can occur in all skin types, although it is more common in darker skin tones. It affects both men and women equally. Luckily, PIH is not a true scar.

PIH and Acne

A postinflammatory hyperpigmentation macule often is the remnant of an inflamed acne lesion. PIH macules can follow relatively minor pimples and papules, in addition to more serious lesions. However, the more inflamed a breakout, the larger and darker the PIH macule tends to be. Picking or popping a pimple increases the chance of developing postinflammatory hyperpigmentation.

You can identify postinflammatory hyperpigmentation by carefully examining the skin. PIH macules can be a range of colors, however, the skin will not be pitted or depressed. It may look like a discolored freckle on the skin, or it may present as a larger, dark discoloration of the skin. PIH macules may look shiny, or like "new skin."

Treating PIH

Most acne sufferers are relieved to learn that postinflammatory hyperpigmentation is not scarring. PIH will fade away over time, even without treatment. It can take three to 24 months for PIH to fully fade, although in some cases it may take longer. The length of time it takes for PIH to fade depends on how dark the PIH macule is compared to your skin tone. The bigger the contrast between the macule and your natural skin tone, the longer it will take to fade.

There are treatment options available to help fade postinflammatory hyperpigmentation more quickly. However, your acne should be under control before beginning any treatment for PIH. Otherwise, each new pimple could cause another PIH macule, reducing the effectiveness of treatment.

Whatever treatment option you choose, understand that improvement will take time. Think in terms of months rather than weeks. Also, many dermatologist recommend using a broad-spectrum sunscreen daily. The sun may darken the discolorations and increase fading time.

Over-the-Counter Treatments
Mild cases of postinflammatory hyperpigmentation may respond well to over-the-counter products. There is a plethora of "brightening" treatment products on the market today. Many use a combination of alpha and beta hydroxy acids (including glycolic acid), vitamin A, vitamin C, and other ingredients to exfoliate the skin. Others, such as M.D. Forte Skin Bleaching Gel, use lightening agents to fade discolorations.

There has been some indication that N-acetyl glucosamine and niacinamide may reduce postinflammatory hyperpigmentation. However, more studies must be completed to verify these findings. N-acetyl glucosamine and niacinamide can be found in products such as Olay® Definity®.

Hydroquinone
Hydroquinone is a widely used treatment for postinflammatory hyperpigmentation. It is available over-the-counter at 1% to 2% strength, and in 3% to 4% 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.

Hydroquinone creams should be carefully applied to darkened areas only, to prevent the unwanted lightening of your natural skin color. Hydroquinone may cause irritation in sensitive individuals. It's worth talking to your doctor before beginning hydroquinone treatment.

Topical Retinoids
Retinoids, such as tretinoin and tazarotene, are often prescribed to acne patients. Retinoids help clear acne by speeding up cell turnover rates. It is this rapid exfoliation that can also help clear PIH. Retinoid creams include Retin-A, Tazorac, and Differin. The fact that they lessen postinflammatory hyperpigmentation as they treat acne breakouts is an added benefit for many people.

Obvious results may not be apparent for several weeks to several months after beginning treatment. Topical retinoids may cause excessive dryness, redness, and/or irritation, which may in turn increase hyperpigmentation. Let your doctor know right if you experience any of these side effects.

Glycolic Acid
Glycolic acid is an alpha hydroxy acid found in a plethora of skin care products. It effectively exfoliates the skin, helping to lighten postinflammatory hyperpigmentation. Available in cleansers, creams, and gels, glycolic acid not only helps improve postinflammatory hyperpigmentation, but also leaves your skin smooth and soft.

Cleansers, gels, pads, and lotions containing glycolic acid are available over-the-counter. Higher concentrations are available with a prescription only. As with all products, improvement may not be seen for several months. Monitor your skin for irritation, and inform your doctor if it occurs.