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Hyperpigmentation is the appearance of dark spots on the skin caused by over-production of melanin, the chemical that determines skin color. While a darker complexion confers some advantage in protection from the sun and fewer signs of aging, it comes with a vulnerability to over-exposure to the sun that can cause dark spots.
What causes PIH?
Post-inflammatory hyperpigmentation (PIH) occurs when the skin reacts to an injury by becoming inflamed. The inflammation triggers production of more melanin in the skin, although it is produced unevenly in spots or patches, and not across the entire area of the skin. In addition to exposure to sunlight, other causes of PIH can be autoimmune thyroid disorders and photosensitizing drugs.
If over-production of melanin occurs in the upper layers of skin, the spots are a darker shade of brown. If in the lower layers of skin, a gray or blue discoloration appears. PIH is most common among people of African, Asian, Latin or Indian origin, although it can occur in both men and women of all skin colors.
Types of PIH
Diffuse hyperpigmentation can also be a symptom of underlying conditions such as:
- Addison’s disease
- chromosome 14 trisomy
- Hay-Wells syndrome
- other diseases 1
Your physician can determine whether it’s PIH or symptomatic in nature.
Drugs that cause PIH
Several kinds of prescription drugs are known to induce hyperpigmentation, among them amiodarone, antimalarials, bleomycin and cancer chemotherapy drugs such as:
- cyclophosphamide dactinomycin
Other triggering drugs are desipramine, hydroquinone, phenothiazines and tetracyclines.
Treating acne scars
Besides over-exposure to the sun, common causes of PIH are scratches, bruises, cuts or burns -- as well as acne in people with darker skin. In many cases, PIH will fade over time. However, there are treatments, such as hydroquinone, that can restore your skin to its natural condition and lighten the dark areas. Although lower strength hydroquinone may be purchased without a prescription, you need to see your dermatologist for a stronger ointment.
Retinoids are drugs that treat acne and the PIH that often results. A derivative of vitamin A, retinoids such as Retin-A has proven effective in treating PIH in people with brown skin. These drugs need to be used sparingly and under the care of a dermatologist. Other drugs that are effective include azelaic acid and glyciolic acid. Chemical peels and microdermabrasion are other methods of treatment.
Microdermabrasion is a cosmetic procedure that involves spraying the dark spots with very small crystals to scrub away the surface pigmentation and remove the dead skin. For people with sensitive skin and for many with brown skin, this method of treatment is well tolerated and effective when used in a dermatologist’s office.
There are two primary types of PIH -- melasma, or dark brown, clearly delineated, symmetrical areas of hyperpigmentation on the face that affect pregnant women and those taking oral contraceptives; and lentigenes, which are flat, darker spots caused by long-term sun exposure. The inflammation triggers production of more melanin in the skin, although it is produced unevenly in spots or patches, and not across the entire area of the skin. However, there are treatments, such as hydroquinone, that can restore your skin to its natural condition and lighten the dark areas.
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