Formulation and Evaluation of Herbal Aromatherapy, Hydrogen Patch Using Orange Peel Essential Oil

Aromatherapy, an established branch of complementary medicine, employs volatile plant-derived compounds to promote psychological and physiological wellness. This review comprehensively examines the formulation and evaluation of a novel herbal aromatherapy hydrogen patch incorporating orange peel essential oil (OPEO). The patch represents an innovative transdermal delivery system designed to simultaneously harness the therapeutic benefits of Citrus sinensis essential oil aromatherapy and molecular hydrogen (H₂) — both recognized for their potent antioxidant, anti-inflammatory, and anxiolytic properties. The review discusses the phytochemical profile of orange peel essential oil (particularly d-limonene, linalool, and myrcene), mechanisms of olfactory and transdermal action, excipient selection, patch fabrication methodologies (matrix and reservoir types), and critical quality control parameters including drug content uniformity, moisture vapor transmission rate (MVTR), flux studies, skin irritation assessments, and in vitro/in vivo evaluation. Current evidence supports that the synergistic combination of H₂ and OPEO in a patch format offers promising pharmacological advantages over single-modality approaches, including enhanced antioxidant activity, improved mood regulation, and sustainable slow release. This paper also identifies research gaps and future directions for clinical translation.