Skin & Regeneration
What Is Post-Inflammatory Hyperpigmentation?
Post-inflammatory hyperpigmentation (PIH) can leave a darker mark after skin injury or inflammation. DermNet describes this pigmentation as temporary and often located where the earlier condition healed. Melanin may settle in skin cells or deeper in the dermis. Appearance alone may not identify a mark; a changing existing mole needs separate medical assessment.
- PIH follows skin injury or inflammation and often appears at the site of the earlier condition.
- Melanin can be deposited in keratinocytes, which are skin cells, or in the dermis.
- A biopsy sometimes helps with diagnosis, but not every mark requires one.
- A change in an existing mole’s shape or size is a reason to seek assessment, independent of PIH.
The mark follows an earlier skin change
DermNet links PIH to an earlier injury or inflammatory condition, often at the site where it healed. History and location offer clues, but a brown spot still needs examination for diagnosis.
DermNet notes that PIH may last longer in darker skin and that sunlight can darken the patches.
Where melanin is deposited in the skin
Injury can affect the epidermis, the outer skin layer, the dermis beneath it, or both. DermNet describes melanin deposited in keratinocytes or in the dermis after such injury. This helps explain a mark that remains after inflammation has settled.
Appearance does not always settle the diagnosis
DermNet says a biopsy is sometimes needed to diagnose PIH. It does not call for a biopsy in every suspected case. History and examination remain part of deciding what a spot represents.
When an existing mole changes
Seoul National University Hospital advises medical assessment when an existing pigmented mole changes shape or size. That is a warning sign for pigmented lesions that may look similar, not evidence that PIH turns into skin cancer.
References
- DermNet New Zealand. “Postinflammatory hyperpigmentation.” DermNet.
- Seoul National University Hospital. “피부암” (in Korean). SNUH health information.
Frequently asked questions
Is a brown patch where dermatitis healed necessarily post-inflammatory hyperpigmentation?
DermNet describes post-inflammatory hyperpigmentation (PIH) as pigmentation following injury or inflammation, often at the site of the healed condition. That sequence is a clue, but appearance and location alone do not confirm a diagnosis.
Which skin layers are involved in PIH?
DermNet describes melanin being deposited in keratinocytes or in the dermis after damage to the epidermis, dermis, or both. This explains how a mark can remain after an inflammatory episode.
Does everyone with PIH need a skin biopsy?
No such general rule follows from the source. DermNet says a diagnosis is sometimes reached only after a skin biopsy; it does not say every case requires one.
When should a spot that looks like pigmentation be checked?
Seoul National University Hospital advises medical assessment when an existing pigmented mole changes shape or size. This is a general warning sign for a skin lesion, not a claim that PIH becomes skin cancer.