Efficacy of Essential Oils in Pain: A Systematic Review and Meta-Analysis of Preclinical Evidence

Abstract

Background: The demand for essential oils (EOs) has been steadily growing over the years. This is mirrored by a substantial increase in research concerned with EOs also in the field of inflammatory and neuropathic pain. The purpose of this present systematic review and meta-analysis is to investigate the preclinical evidence in favor of the working hypothesis of the analgesic properties of EOs, elucidating whether there is a consistent rational basis for translation into clinical settings.Methods: A literature search has been conducted on databases relevant for medical scientific literature, i.e., PubMed/MEDLINE, Scopus, and Web of Science from database inception until November 2, 2020, following the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) criteria for systematic reviews and meta-analyses.Results: The search was conducted in order to answer the following PICOS (participants/population, interventions, comparisons, outcomes, and study design) question: are EOs efficacious in reducing acute nociceptive pain and/or neuropathic pain in mice experimental models? The search retrieved 2,491 records, leaving 954 studies to screen after the removal of duplicates. The title and abstract of all 954 studies were screened, which left 127 records to evaluate in full text. Of these, 30 articles were eligible for inclusion.Conclusion: Most studies (27) assessed the analgesic properties of EOs on acute nociceptive pain models, e.g. the acetic acid writhings test, the formalin test, and the hot plate test. Unfortunately, efficacy in neuropathic pain models, which are a more suitable model for human conditions of chronic pain, had fewer results (only three studies). Moreover, some methodologies raised concerns in terms of the risk of bias. Therefore, EOs with proven efficacy in both types of pain were corroborated by methodologically consistent studies, like the EO of bergamot, which should be studied in clinical trials to enhance the translational impact of preclinical modeling on clinical pain research.

Preclinical Characterization of Antinociceptive Effect of Bergamot Essential Oil and of Its Fractions for Rational Translation in Complementary Therapy

“…The translational use of essential oils still requires preclinical validation in support of clinical efficacy and safety. However, this evidence has already been achieved for bergamot essential oil (BEO) [1]. BEO is produced from the cold pressing of the epicarp and the partly cold pressing of the mesocarp of fresh bergamot fruit (Citrus bergamia Risso et Poiteau), and it is composed of a volatile fraction (93-96%) that includes monoterpene and sesquiterpene hydrocarbons, of which one of the most important is limonene.…”

Translational Value of the Transdermal Administration of Bergamot Essential Oil and of Its Fractions

“…In fact, the extraction of limonene, linalool, and linalyl acetate has been highly studied, and novel techniques, such as enzyme-mediated pervaporation, have been suggested [ 5 ]. At variance with most studies on essential oils in pain [ 6 ], the translational clinical efficacy and safety of BEO into the clinic is supported by its strong preclinical evidence of analgesic efficacy. This was achieved through studies meeting the best criteria for in vivo basic research, according to the guidelines for Animal Research: Reporting In Vivo Experiments (ARRIVE) [ 7 ], the Systematic Review Center for Laboratory Animal Experimentation (SYRCLE) risk of bias (RoB) tool [ 8 ], and the Collaborative Approach to Meta-Analysis and Review of Animal Data from Experimental Studies (CAMARADES) checklist for study quality [ 9 ].…”

Exploring Pharmacological Mechanisms of Essential Oils on the Central Nervous System

“…As mentioned earlier, the major constituents of lavender oil are believed to exert their effects through interactions with the GABAergic system [ 11 ]. Concerning anxiety relief and stress management, a study conducted in 2005 indicated a decline in anxiety, stress, and improved mood following inhalation of the scent of lavender oil [ 12 ].…”