Post-inflammatory hyperpigmentation and hypopigmentation

What is post-inflammatory hyperpigmentation and hypopigmentation?

Hyperpigmentation on the foot

Post-inflammatory hyperpigmentation and hypopigmentation (PIH) occur when the skin changes colour after experiencing inflammation or trauma. Inflammation can include a skin irritation or infection, for example, and trauma can include a scrape from an object.

• Hyperpigmentation means that the skin looks darker than normal (often brown to grey). This is the more common response after inflammation.
• Hypopigmentation means that the skin looks lighter than normal.

PIH can occur almost anywhere on the body and in many shapes and sizes. The size and location of PIH depend on the cause of the initial inflammation.

How does PIH affect the body?

PIH only changes how the skin appears. It does not harm the skin or the body. Most cases resolve within six months, but sometimes it can take longer for skin colour to even out.

What causes the skin to change colour?

The change in colour results from a change in the amount of melanin (skin colour pigment) that the body produces when the skin becomes inflamed. As the inflammation clears, the colour change is easier to notice. In some ethnicities, especially those with darker skin, the colour change might be more obvious.

Examples of conditions that can cause PIH

• Eczema
• Psoriasis
• Skin allergies (contact dermatitis)
  
• Trauma (injury) to the skin
  
• Insect bites
• Acne

How is PIH diagnosed?

Your doctor can diagnose PIH by examining your child's skin and asking about your child’s medical history, for example a history of skin inflammation or redness from eczema or mosquito bites. Some doctors may also use a special black light (called a Wood’s lamp) to help them confirm a diagnosis of PIH.

How is PIH treated?

Your child will not need any treatment for PIH. Colour changes can take many months to disappear, but it eventually happens on its own.

In general, treating the cause of inflammation or redness early on can prevent some of the colour change due to PIH. For example, if your child’s skin changes colour due to a skin disease, such as eczema, your doctor may recommend a treatment to help control those symptoms to prevent further changes.

You can help your child's skin look more even in colour by moisturizing it, especially if it is dry, and protecting it from the sun with clothing and sunscreen (with both UVA and UVB sunblock). Protecting your child's skin from sun damage is also an important part of general sun safety.

When to see a doctor for PIH

See your child’s doctor if:

• your child’s PIH is getting larger or looks different over time
• you think your child has ongoing, underlying skin problems, such as eczema.