What is post-inflammatory hyperpigmentation?
Post-inflammatory hyperpigmentation is the most common form of abnormal darkening of the skin. Through inflammation of the skin, an excess of melanin pigment is produced. The dark discolouration arises exactly where the inflammation was, and becomes visible once the inflammation disappears. It is often experienced as particularly distressing for cosmetic reasons.
With which types of inflammation does it occur?
Common causes: acne, eczema, bacterial skin infections (such as impetigo), yeast infections, injury and insect bites.
Less common causes: psoriasis, lichen planus, lupus erythematosus, drug reactions, and rashes from a viral infection.
Who gets it?
Post-inflammatory hyperpigmentation can arise at any age. People with a dark skin type have a strongly increased risk; in them the pigmentation is often darker and more long-lasting than in people with a light skin type.
What does it look like?
Depending on the person’s skin colour and the depth at which the extra pigment lies, the colour can vary from light brown to dark brown to grey-blue. The deeper the pigment lies, the greyer the colour. When the spot is also exposed to the sun (on the face, for example), the pigmentation can become extra dark.
How is it treated?
Post-inflammatory hyperpigmentation is usually difficult — or even impossible — to treat. When the inflammation has disappeared and does not return, the pigmentation will in many cases disappear by itself, but very slowly. Especially when the pigment lies superficially in the skin, the chance of spontaneous improvement is reasonably good; deep-lying pigment rarely disappears.
For superficial forms, treatment with a bleaching cream (for example hydroquinone cream) can be considered. Unfortunately the risk of complications with this therapy is fairly high precisely in people with a dark skin type, and the same applies to laser treatment, which should therefore be carried out by someone with a lot of experience. Always seek good advice and guidance from a dermatologist before any treatment. Protecting the affected skin from the sun helps prevent the pigmentation becoming darker.
When to see a doctor
See your GP or a dermatologist if dark marks persist and bother you, particularly if you have a darker skin type, and before starting bleaching creams or laser — these need experienced guidance to avoid worsening the pigmentation. Treating the underlying inflammation (such as acne or eczema) early gives the best chance of preventing new marks.