Axillary hyperpigmentation is frequent in dark skin population, is possible a type of postinflammatory hyperpigmentation present in phototypes IV to VI. Previous reports have described increased intensity of Masson-Fontana, anti-tyrosinase and/or anti-TRP1 staining, indicative of melanocyte stimulation and increased melanin production, but the exact mechanism is unknown. The hair plucking, the rubbing of clothes on skin and physical stimulation from washing and drying the underarm are factors implicated. The objective of our study is evaluate the depigmenting effect of topical niacinamide versus desonide in axillary hyperpigmentation through the histochemistry and immunohistochemistry staining.~The study population will include at least 30 axillas with hyperpigmentation in a population with phototype III-V and aged 18-50 years old. Informed consent will be obtained from the patients, under approval by the local ethical committee (Institutional Review Board). The patients are going to be randomly assigned to receive 4% niacinamide, 0.05% desonide or placebo daily once at night. None hygienic habit is going to be modified. Volunteers will be evaluated at baseline and 9 weeks later, with histochemical and immunohistochemical analysis (biopsies), colorimetric value axis L*, a*, b* (Chromameter CR-300, Minolta, Osaka, Japan), Transepidermal Water Loss (TEWL) by means of an evaporimeter (Dermalab, Cortex Technology, Denmark), clinical assessment and photography control.~Statistical analysis was performed using t student, the level of significance was set at 5%. And clinical evaluation will be analysed by means of chi square test.
Axillary hyperpigmentation is a frequent consultation in dark skin populations although its exact prevalency is unknown. Currently, there are not studies about physiopathology and treatment for this entity. The objective is to evaluate the depigmenting effect of topical 4% niacinamide versus 0.05% desonide in axillary hyperpigmentation.~At least 30 axillas with hyperpigmentation in individuals of phototype III-V, aged 18-50 years are going to be randomly assigned to receive niacinamide, desonide or placebo daily. No hygienic habits will not be modified. Volunteers will be evaluated at baseline and for 9 weeks, by means of histological, histochemical and immunohistochemistry analysis, as well as Transepidermal Water Loss (TEWL), colorimetry, clinically and by photography control.