BackgroundAxillary 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.MethodsTwenty-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.ResultsBoth 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.ConclusionNiacinamide and desonide showed depigmenting properties in women with axillary hyperpigmentation. These findings may be explained by their antimelanogenic and anti-inflammatory properties, respectively.