Post-Inflammatory Hyperpigmentation (PIH): Causes, How to Fade It, and Ingredients That Help
Post-inflammatory hyperpigmentation (PIH) is a darker patch of skin that appears after the skin has been inflamed, for example dark marks from acne, eczema, scrapes or insect bites. It is very common in Asian and darker skin tones, because inflammation prompts pigment-producing cells to make more melanin than normal. The key point: PIH is different from redness and scars, and it can fade with the right treatment together with strict sun protection.
In this article, a dermatologist explains what causes PIH, how it differs from post-inflammatory redness (PIE), which ingredients really help, and how it is treated in the clinic.
Quick Facts: Post-Inflammatory Hyperpigmentation (PIH)
What it is: darker skin (brown to black) left after inflammation, such as dark marks from acne.
Cause: inflammation stimulates pigment-producing cells to make too much melanin.
Difference from redness (PIE): PIH is brown or dark, while PIE is red from blood vessels.
Helpful ingredients: niacinamide, vitamin C, retinoids, azelaic acid, tranexamic acid and arbutin.
Most important: daily sun protection, because sun makes dark marks darker and slower to fade.
What causes post-inflammatory hyperpigmentation (PIH)?
PIH develops when the skin has been inflamed and pigment-producing cells (melanocytes) are stimulated to make more melanin than normal. Melanin builds up in the area that was inflamed and becomes a darker mark. Factors that cause it or make it darker include:
Inflamed acne and picking or squeezing pimples are the most common cause of dark marks from acne.
Eczema, scrapes, insect bites or other skin conditions that inflame the skin.
Sun exposure without sun protection, which stimulates pigment so marks get darker and fade more slowly.
Darker skin tones, which develop PIH more easily and more noticeably.
Repeated scratching or irritation, which prolongs the inflammation.
How is PIH different from PIE and scars?
Marks after acne and inflammation come in several types. Telling them apart helps you choose the right treatment:
Post-inflammatory hyperpigmentation (PIH): brown to black marks caused by melanin, which usually respond to pigment-reducing ingredients and sun protection.
Post-inflammatory erythema (PIE): pink or red marks from tiny blood vessels, more often seen in fair skin. Treatment differs from PIH, for example vascular lasers.
Acne scars: a change in skin texture (indented or raised), not just colour, which needs specific procedures.
Melasma: brown patches linked to hormones and sun, not caused by a single area of inflammation.
A simple check: if the mark fades when you stretch the skin, it is usually redness (PIE), but if it stays dark brown, it is usually PIH.
Ingredients that really help fade dark marks
Ingredients with research support for reducing PIH include:
Niacinamide: reduces pigment transfer to the skin surface and calms inflammation, with low irritation.
Vitamin C: an antioxidant that helps brighten the skin.
Retinoids: speed up skin cell turnover and help dark marks fade faster.
Azelaic acid: reduces pigment and suits acne-prone skin.
Tranexamic acid and arbutin: help inhibit pigment production.
Exfoliating acids (AHA/BHA): help shed skin cells that hold pigment.
These ingredients need to be used consistently for several weeks to several months, and always together with sunscreen.
How to treat post-inflammatory hyperpigmentation
Strict daily sun protection is the most important step, because sun makes dark marks darker and slower to fade.
Treat the cause of the inflammation, for example by keeping acne under control and not picking or squeezing pimples.
Use pigment-reducing products such as niacinamide, vitamin C, retinoids or azelaic acid, consistently.
Clinic procedures such as chemical peeling or pigment-reducing lasers, for marks that are dark or long-standing.
Avoid repeated irritation, because new inflammation causes more dark marks.
Does PIH go away on its own, and how long does it take?
Most PIH fades on its own over time, but it often takes several months to a year or more, especially for deeper marks or in darker skin. Sun protection and pigment-reducing ingredients clearly help it fade faster. On the other hand, frequent sun exposure or repeated inflammation can make the marks last longer or look darker.
Signs you should see a dermatologist
Dark marks that are widespread, dark, or just will not fade despite using creams.
Ongoing inflamed acne that keeps causing new dark marks.
You cannot tell whether it is PIH, redness, melasma or acne scarring, which are treated differently.
You want to speed up fading safely with procedures such as lasers or peels.
Common myths about PIH
"Dark marks from acne will go away on their own, so I don't need to do anything." They can fade on their own but very slowly, and without sun protection they may last longer or get darker.
"The harder I scrub my face, the faster the marks fade." Harsh scrubbing inflames the skin and causes more dark marks.
"Squeezing pimples makes the marks go away faster." Picking and squeezing causes more inflammation and more noticeable dark marks.
"A dark-mark cream works right away." It must be used consistently for several weeks to several months. Consistency and sun protection matter most.
Frequently asked questions about PIH
What causes dark marks from acne (PIH)?
Skin inflammation, such as from acne or picking pimples, stimulates pigment-producing cells to make too much melanin, leaving brown to black marks where the skin was inflamed. It is common and more noticeable in darker skin.
What is the difference between PIH and PIE?
PIH is a brown or black mark caused by melanin, while PIE is a pink or red mark from tiny blood vessels. If the mark fades when you stretch the skin, it is usually redness. The two are treated differently, so it is important to tell them apart.
Does PIH go away on its own?
Most fades on its own but it takes several months to a year or more, especially in darker skin. Sun protection and pigment-reducing ingredients help it fade faster, while sun exposure and repeated inflammation make it last longer.
Which ingredients really help fade dark marks?
Those with research support include niacinamide, vitamin C, retinoids, azelaic acid, tranexamic acid, arbutin and AHA/BHA exfoliating acids. They must be used consistently and together with sun protection.
What clinic treatments are there for dark marks?
Options include chemical peeling and pigment-reducing lasers, which help marks fade faster when they are dark or long-standing. They should be done under the care of a dermatologist for safety.
Does sun protection really help with dark marks?
Yes, and it is the most important step. Sun stimulates pigment production, making dark marks darker and slower to fade. Applying sunscreen every day helps marks fade faster and prevents new ones.
If you have acne dark marks or PIH that are long-standing or will not fade, see a dermatologist for an assessment and a treatment plan suited to your skin. Consult a specialist dermatologist at Siam Dermatology, call +66 61 448 7000 or LINE @siamderm
Written by Dr. Patara Voravutinon, Dermatologist · Last reviewed 22 August 2026
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