INTRODUCTION
Post-inflammatory hyperpigmentation (PIH) is a reactive process resulting from increased melanin or abnormal distribution of melanin, secondary to inflammatory skin conditions such as acne, atopic dermatitis, contact dermatitis, and psoriasis, as well as external factors such as burns and radiation therapy. An understanding of treatment strategies for PIH is essential, as it has a large impact on the quality of life.1 Though there are many therapeutic strategies for hyperpigmentary conditions such as melasma that are described in the literature, fewer studies specifically address PIH. Thus, we conducted a literature review on PubMed using key words “post-inflammatory hyperpigmentation†OR “postinflammatory hyperpigmentation.†Studies that did not specifically address PIH and articles that were not published in English were excluded. Additional studies were obtained by scanning references. This review adds to the current literature by discussing the evidence for topical therapies, chemical peels, and laser therapy used specifically for hyperpigmentation from PIH.
Topical Therapies
Retinoids
Many studies have shown that topical retinoids can be effective for treatment of PIH associated with acne, particularly in darker skin types (Table 1). A significantly greater reduction in clinical assessment of PIH compared to placebo has been demonstrated in randomized controlled trials of patients using tretinoin 0.1% for 50 weeks2 and tazarotene 0.1% for up to 18 weeks.3 Similarly, in a study of 65 patients with acne, use of adapalene 0.1% gel for 12 weeks resulted in a reduction of hyperpigmented macules and density of hyperpigmentation in 2/3 of the “highly pigmented†cases.4 Furthermore, two studies address the use of topical retinoids in combination with other topical therapies. Combination of topical clindamycin 1.2% and tretinoin 0.025% gel for patients with facial acne and PIH did not significantly reduce the chromameter measurement of melanin or clinical assessment of PIH compared to placebo.5 However, in 50 patients with acne (60% had PIH) who applied a 0.3% adapalene gel/benzoyl peroxide 2.5% gel daily, 75% had no PIH or very mild PIH at 16 weeks, with the average decrease in PIH severity score of 27%.6 Thus topical retinoids alone may be effective for treating acne-induced PIH, but optimal combination therapies are not well-established in the literature.
Hydroquinone combinations
Studies that address the use of hydroquinone for PIH demonstrate that it is useful when combined with a retinoid (Table 1). In a combination therapy of 5% hydroquinone, 7% lactic acid ointment, and either 0.1% all trans retinoic acid ointment or gel applied twice daily in 8 patients with PIH, 4 had a “good†response.7 Two studies combined microencapsulated hydroquinone 4% with retinol 0.15% twice daily for 12 weeks; one study found that the melanin content as measured by spectrophotometer was significantly reduced by week 4;8 both found that there was a significant improvement in clinically assessed disease severity compared to baseline by week 4.8,9
Topical Therapies
Retinoids
Many studies have shown that topical retinoids can be effective for treatment of PIH associated with acne, particularly in darker skin types (Table 1). A significantly greater reduction in clinical assessment of PIH compared to placebo has been demonstrated in randomized controlled trials of patients using tretinoin 0.1% for 50 weeks2 and tazarotene 0.1% for up to 18 weeks.3 Similarly, in a study of 65 patients with acne, use of adapalene 0.1% gel for 12 weeks resulted in a reduction of hyperpigmented macules and density of hyperpigmentation in 2/3 of the “highly pigmented†cases.4 Furthermore, two studies address the use of topical retinoids in combination with other topical therapies. Combination of topical clindamycin 1.2% and tretinoin 0.025% gel for patients with facial acne and PIH did not significantly reduce the chromameter measurement of melanin or clinical assessment of PIH compared to placebo.5 However, in 50 patients with acne (60% had PIH) who applied a 0.3% adapalene gel/benzoyl peroxide 2.5% gel daily, 75% had no PIH or very mild PIH at 16 weeks, with the average decrease in PIH severity score of 27%.6 Thus topical retinoids alone may be effective for treating acne-induced PIH, but optimal combination therapies are not well-established in the literature.
Hydroquinone combinations
Studies that address the use of hydroquinone for PIH demonstrate that it is useful when combined with a retinoid (Table 1). In a combination therapy of 5% hydroquinone, 7% lactic acid ointment, and either 0.1% all trans retinoic acid ointment or gel applied twice daily in 8 patients with PIH, 4 had a “good†response.7 Two studies combined microencapsulated hydroquinone 4% with retinol 0.15% twice daily for 12 weeks; one study found that the melanin content as measured by spectrophotometer was significantly reduced by week 4;8 both found that there was a significant improvement in clinically assessed disease severity compared to baseline by week 4.8,9
