Post-Inflammatory Hyperpigmentation (PIH) - Symptoms, Causes & Treatment
Medically reviewed by Dr. Anand S. Urhekar, MD, MD Pathology, Clinical Advisor · Last updated July 2026
Flat brown, grey or purple marks left behind after skin inflammation — most commonly acne, eczema, a burn or an insect bite. The inflammation stimulates melanocytes to overproduce pigment, which then takes months to clear. PIH is far more common and longer-lasting in Fitzpatrick skin types IV–VI.
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Quick Answer
Post-inflammatory hyperpigmentation is a flat brown, grey or violet mark left after acne, eczema or another inflammatory skin problem. It is not a scar — the skin texture is normal — and it fades on its own over three to twenty-four months. Daily broad-spectrum SPF 30+ is the single most important step; azelaic acid, niacinamide, retinoids, tranexamic acid and vitamin C speed fading.
Symptoms
- Flat brown, grey-brown or violet patches with normal skin texture
- Located exactly where the previous spot or rash was
- No raised or indented scarring
- Darker and more persistent in richly pigmented skin
- Deepens with sun exposure
Causes & Risk Factors
- Acne, especially inflamed papules and nodules
- Eczema, psoriasis and contact dermatitis
- Insect bites, burns and cuts
- Picking or squeezing spots
- Cosmetic procedures such as aggressive peels or laser
Treatment & Management
- Daily broad-spectrum SPF 30–50, reapplied — prevents further darkening
- Azelaic acid 10–20%
- Niacinamide 4–10%
- Topical retinoids (adapalene, tretinoin)
- Vitamin C, tranexamic acid, or prescription hydroquinone under medical supervision
- Treating the underlying inflammation first
When to See a Doctor
See a doctor if marks are still darkening after the original spot has healed, if you cannot control the underlying acne or eczema, or if the pigmentation is raised, itchy or has an irregular border — the latter needs assessment to exclude other diagnoses.
Frequently Asked Questions
How long does post-inflammatory hyperpigmentation take to fade?
Superficial (epidermal) PIH generally fades over 3–12 months. Deeper dermal pigment, which looks more grey or blue, can take 12–24 months or longer. Consistent sunscreen shortens the timeline substantially.
Is PIH the same as an acne scar?
No. PIH is a flat colour change with normal texture and it fades. A true acne scar involves loss or excess of tissue — a pit or a raised lump — and it does not fade on its own.
Does sunscreen really matter for dark marks?
Yes. UV directly stimulates the melanocytes that are already overactive. Without daily SPF, treatments such as azelaic acid or retinoids are working against a constant re-darkening signal.
Medical References
Information on this page is sourced from and verified against reputable medical resources:
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Medical Disclaimer: This information is for educational purposes only and is not intended as medical advice. The content on this page should not be used to diagnose or treat any health problem. Always consult with a qualified healthcare professional for proper medical evaluation, diagnosis, and treatment of your condition.