Nanoemulsions for Skin Delivery of Essential Oils: A Systematic Review

Essential oils (EOs) are recognized for their multiple health benefits. However, their high volatility, low stability, and limited water solubility limit their effective application. This systematic review aims to assess the use of nanoemulsions as delivery systems for the topical administration of EOs, highlighting their efficacy, safety, and limitations. A literature search was conducted in the PubMed, Scopus, and Web of Science databases for studies published in English before February 2025, following the PRISMA 2020 guidelines. Studies limited to in vitro or ex vivo assays, using isolated EO components, or involving non-topical applications were excluded. Twenty-two articles were included in this review, comprising EOs from 18 plant species, and applied in animal or human in vivo models for wound healing (n = 6), anti-inflammatory/analgesic effects (n = 5), cosmetic (n = 6), and transdermal delivery/permeation enhancer (n = 5). Nanoemulsions improved EOs' bioactivities, particularly their anti-inflammatory, antioxidant, and antimicrobial effects, by enhancing skin permeation, bioavailability, and skin barrier function, reducing skin irritation, and allowing a controlled release. However, the overall risk of bias, assessed using the SYRCLE and RoB 2 tools, was considered high, and the studies' heterogeneity limited direct comparisons. Therefore, further well-designed preclinical and clinical trials are needed to validate these findings and assess the potential of the EOs nanoemulsions for topical use.