Background/purpose: Cutaneous hyperpigmentation occurs in multiple conditions. There is a strong need for the improvement of hyperpigmentation especially among Asian women. However, the effect of existing skin-lightening agents is not sufficient. One reason attributes to the limited capability of active agents to be delivered transepidermally. Ultrasound is one promising approach to enhance transepidermal transport. In this work, we investigate the effect of the use of high-frequency ultrasound together with coupling gel containing skin-lightening agents (ascorbyl glucoside and niacinamide) on facial hyperpigmentation in vivo in Japanese women.
Methods: The effect of ultrasound on the absorption of skin-lightening agents into the stratum corneum was evaluated in a tape-stripping method on human forearms in vivo. The skin efficacy was assessed in a facial clinical trial involving 60 subjects with hyperpigmentation in a paired design. Subjects were assigned to two groups, each group using two treatments (one on each facial cheek): (1) skin-lightening gel with ultrasound vs. no treatment or (2) skin-lightening gel with ultrasound vs. skin-lightening gel treatment. Changes in facial hyperpigmentation were objectively quantified by computer analysis and visual grading of high-resolution digital images of the face in addition to the subjective assessment via questionnaire.
Results: Ultrasound radiation enhanced the absorption of skin-lightening agents in the stratum corneum in a radiation-time-dependent manner. In the facial clinical trial, use of ultrasound radiation together with the skin-lightening gel significantly reduced facial hyperpigmented spots compared with both no treatment and skin-lightening gel alone after 4 weeks.
Conclusions: The data suggest that use of high-frequency ultrasound radiation together with skin-lightening gel is effective to reduce hyperpigmentation via enhancing transepidermal transport of skin-lightening agents.