Louise Gagnon is a medical writer and editor based in Oakville, Ontario, Canada.
Therapies that combine hydroquinone and other compounds can be prescribed to treat PIH, which can appear secondary to eczema, acne.
"It's a condition that we don't know a lot about," Dr. Rendon says. "It can be caused by a lot of different conditions that can trigger the pigmentary aspects of it."
Patients may present with conditions such as eczema or acne. Once those conditions heal, they may present with PIH, particularly after acne has disappeared.
PIH is more common in darker-skinned and ethnic individuals, Dr. Rendon says. PIH can also result from trauma to the skin, such as a cut; at the site of injury or nearby; or as a result of inflammation to the skin, which can originate from a procedure such as laser therapy to remove hair.
Dr. Rendon adds there are special settings on a laser device that be chosen to minimize the risk of an inflammatory reaction.
"It's better to use lower fluences, lower energies and lower concentrations when treating darker-skinned populations to avoid postinflammatory hyperpigmentation," she says.
Standard treatment for PIH is typically hydroquinone cream, which is available in a 2 percent formulation over the counter and a 4 percent prescription formulation. Newer formulations of hydroquinone, either dual or triple combination, add other components to optimize outcomes, Dr. Rendon says.
"There is a product with hydroquinone and retinol, an active form of vitamin A, that works better than hydroquinone alone," she says. "There is also a product that is a triple combination that has hydroquinone, tretinoin and mild steroid. The combination products work faster (than hydroquinone alone)."
Herbal remedies, in the form of licorice and mulberry extracts, have been explored to treat PIH and are available as complementary medicines, but the results have not been impressive, according to Dr. Rendon.
Soy proteins, niacinamide, kojic acid and retinoids are all topical compounds that lighten the skin and can be used to treat PIH, Dr. Rendon says. Azelaic acid, available via prescription in the United States, is another topical compound that can treat PIH.
Current research is focusing on the development of anti-inflammatory agents to treat and prevent PIH, according to Dr. Rendon.
Clinicians must be cautious when administering medications to treat PIH, to ensure that the hyperpigmented skin does not become too light and visibly different from the normal skin, she says.
Sunscreens should be used regularly to prevent PIH, and should be used during treatment for PIH to maximize the efficacy of treatment, Dr. Rendon says.
In the case of managing PIH after an appearance of acne, superficial chemical peels and microdermabrasion can be performed to accelerate the healing process in addition to using standard therapy, she adds.
Indeed, adjuvant therapies that promote epidermal turnover allow the skin to exfoliate and block the transfer of melanosomes to keratinocytes, Dr. Rendon says.
The caveat is that a procedure such as a chemical peel can produce further PIH if an inflammatory reaction occurs. Given that risk, it's key that dermatologists, rather than general practitioners, perform such a procedure to avoid irritation or burning of the skin, she says.
Patients may present with PIH to their general practitioner, but it is good practice that patients see a specialist physician to manage PIH.
Of note, prescription topical products for treating PIH are contraindicated in patients who are pregnant, Dr. Rendon says.
Disclosure: Dr. Rendon reports no relevant financial interests.