Post-Inflammatory Hyperpigmentation

What is post-inflammatory hyperpigmentation?

Post-inflammatory hyperpigmentation (PIH) is darkening of the skin that develops after inflammation or injury. It is not a separate disease but a response of the skin, and it is one of the most common reasons people with brown and black skin see a dermatologist.

Who gets it?

Anyone can develop PIH, but it is much more common, more noticeable and longer lasting in people with medium to darker skin tones.

What causes it?

When the skin is inflamed or injured, pigment cells are stimulated to produce extra melanin. The pigment may stay in the outer skin layer, or it may sink into the deeper layer, where cells absorb it and it can persist for a long time.

Common causes include acne, eczema, psoriasis, lichen planus, insect bites, cuts, burns, friction, shaving and waxing, and cosmetic procedures such as laser treatment, chemical peels and microneedling. Picking or scratching the skin makes it more likely. Sun exposure darkens PIH and slows fading.

Is it hereditary or contagious?

PIH is not inherited, although the tendency to develop it is related to skin type. It is not contagious.

What does it look and feel like?

PIH appears as flat patches or spots that are darker than the surrounding skin, in the same places where inflammation or injury occurred. The colour ranges from light brown to dark brown or black when the pigment is in the upper skin, and from grey to blue-grey when it is deeper. It does not cause itch or pain, although the underlying condition may.

How is it diagnosed?

PIH is diagnosed from the appearance and history. Identifying and controlling the underlying cause, such as acne or eczema, is an important part of the assessment, because ongoing inflammation will continue to create new marks.

What are the treatment options?

Dr Mounsey will treat the underlying condition causing the marks, such as acne or eczema, as this is the most important step. Daily broad-spectrum sun protection helps the marks fade more quickly. Lightening treatments can include azelaic acid, retinoid creams, hydroquinone and other brightening agents. Chemical peels may help some people, but need care in brown and black skin. He will explain what to expect, as marks in the deeper layer of the skin fade more slowly.

What is the outlook?

PIH usually fades gradually once the underlying inflammation has settled. Pigment in the upper skin often fades over several months, whereas deeper pigment can take a year or longer and sometimes persists. Sun protection helps marks fade.

More information

The British Association of Dermatologists has a range of patient information leaflets at https://www.skinhealthinfo.org.uk

This page gives general information only and is not a substitute for a consultation. Everyone's skin is different, and what is right for you will depend on your own circumstances. If you are worried about a skin problem, please book an appointment with Dr Mounsey or speak to your GP. If you have a mole or skin lesion that is changing, bleeding or growing quickly, please seek medical advice promptly.