Topical niacinamide 4% and desonide 0.05% for treatment of axillary hyperpigmentation: a randomized, double-blind, placebo-controlled study

Abstract

Background: Axillary hyperpigmentation is a frequent cause of cosmetic consultations in dark-skinned women from tropical areas, including Latin America. Currently, there is no widely accepted treatment for the disorder, but it is usually treated with bleaching agents because it is considered a variant of inflammatory hyperpigmentation. The purpose of this study was to assess the efficacy of niacinamide 4% and desonide 0.05% emulsions compared with placebo in the treatment of axillary hyperpigmentation.

Methods: Twenty-four women aged 19-27 years with hyperpigmented axillae (phototype III-V) were randomly assigned to receive the study treatments in the axillary region. Improvement was assessed at baseline, then clinically and by colorimetry 9 weeks later. Quantitative evaluation including melanin, inflammatory infiltrates, NKI/Beteb, CD1a, CD68, and collagen type IV content was performed by histochemistry and immunohistochemistry, assisted by computerized morphometric analysis.

Results: Both niacinamide and desonide induced significant colorimetric improvement compared with placebo; however, desonide showed a better depigmenting effect than niacinamide. A good to excellent response was achieved in 24% of cases for niacinamide, 30% for desonide, and 6% for placebo. We observed a marked disruption of the basal membrane in axillary hyperpigmentation and an inflammatory infiltrate that improved after treatment. Decreased pigmentation in the desonide-treated axillae was associated with recovery of disruption at the basal membrane.

Conclusion: Niacinamide and desonide showed depigmenting properties in women with axillary hyperpigmentation. These findings may be explained by their antimelanogenic and anti-inflammatory properties, respectively.

Keywords: desonide; niacinamide; post-inflammatory hyperpigmentation.

Figure 1

Effect of niacinamide (n = 16), desonide (n = 16), and placebo (n = 16) on the luminosity change (L*Δ) in axillae treated during the study. Notes: The bar chart shows differences between the group means during the study. *P ≤ 0.05, statistically significant compared with placebo. Both drugs were better than placebo at 9 weeks, but desonide improved the axillary hyperpigmentation better than niacinamide (t-test, P = 0.002).

Figure 2

Physician assessment of improvement in axillary hyperpigmentation at the end of treatment (week 9). Notes: The efficacy of niacinamide and desonide was rated equally for good and excellent response (P = 0.5, and P = 0.8, χ² test). The placebo response was significantly lower compared with both drugs for these categories (P < 0.001, χ² test).

Figure 3

Photographs showing an excellent clinical response to treatment. (A) Axillae in a 22-year-old woman treated with niacinamide (left image). (B) The desonide-treated side in a 25-year-old woman at baseline and after 9 weeks of therapy (right image).

Figure 4

Reduction of epidermal melanin content (Fontana-Masson staining, 400×) after niacinamide and desonide, compared with placebo (first row). Notes: Shown in the second row are representative examples of skin tissues stained with hematoxylin and eosin (200×) where numbers of mononuclear cells are more abundant in the placebo group. Immunohistochemical staining of skin tissues for CD68 cells (100×) and collagen type IV (400×) in the third and fourth row showing a reduction of CD68 expression and increased basal membrane continuity for niacinamide and desonide compared with placebo. Collagen IV interruption sites and CD68 cells are pointed out with arrowheads. Bars show approximate measures. Abbreviations: HE, hematoxylin and eosin staining; FM, Fontana-Masson staining.

Figure 5

(A) Relationship between values in luminosity differences (L*Δ) of the affected axillae, and the percent of basal membrane discontinuity expressed as collagen IV staining for the interventions at the end of the study. A significant association was only evident for desonide (P = 0.01). (B) Relationship between melanin content by Fontana-Masson staining and collagen IV expression for each intervention at the conclusion of the study. Note: The association was significant for desonide and placebo (P = 0.04, for both).