Study of botulinum toxin type A for the treatment of ultraviolet B-induced hyperpigmentation: A prospective, randomized, controlled trial

Background Botulinum toxin type A (BTX-A) has been used experimentally under various dermatological conditions. Recent studies have revealed a preventive effect of BTX-A against ultraviolet B (UVB)-induced skin hyperpigmentation. Objective We examined the effect of BTX-A for the treatment of UVB-induced hyperpigmentation in humans. Material and methods A prospective, double-blind, randomized controlled trial was conducted. UVB irradiation induced five separate hyperpigmented squares on the abdomen. Seven days after irradiation, all squares were randomly assigned to five intervention groups: control, 0.9% normal saline injection, 12 units (1:2.5), 6 units (1:5), and 4 units (1:7.5) of onabotulinum toxin injections. The lightness index (L*), hyperpigmentation improvement score rated by a blinded physician, and participant satisfaction scores were obtained at 14, 21, and 28 days after injection. Results Fifteen participants (mean age 36.9 years, Fitzpatrick skin types III-IV) completed the study. The BTX-A (1:2.5)-treated site had a lower degree of hyperpigmentation at all time points, as measured by mean L* and hyperpigmentation improvement scores. However, there were no statistically significant differences between the groups. Participants were most satisfied with the control site. Conclusion Intradermal BTX-A injection had no therapeutic effect on UVB-induced hyperpigmentation. However, the role of BTX-A injections in the treatment of other hyperpigmentary conditions requires further elucidation.