Looking Back to Move Forward: The Current State of Research on the Clinical Applications of Camphor- and Menthol-Containing Agents

Topically applied compounds containing camphor and menthol have been used to alleviate pain, cold symptoms, and pruritus, historically predominantly in East Asia. Being not studied well, they are less recognized in Western medicine. Given the commonality of pain, pruritus, and cold symptoms in addition to the growing need for non-opioid treatment options, the authors investigated clinical applications of such compounds for their over-counter usage. The purpose was to analyze current clinical research and applications regarding the use of these topical agents. This study involved a bibliometric analysis of peer-reviewed articles, published in English and indexed in PubMed from 2010 to 2022, pertaining to camphor- and menthol-containing compounds. There were 103 results, of which 15 (14.6%) articles were related to the treatment of disorders related to health, such as upper respiratory infection, pain, and pruritus. Excluded were “non-research” articles (e.g., letters to the editor), articles that do not involve human subjects, reports of improper application or misuse (e.g., ingestion), and articles pertaining to intraoral, intranasal, and ophthalmic agents. Of these articles, the originating journals, respective journal impact factor scores, publication years, study designs, and study topics were identified. Underlying trends and themes regarding clinically relevant research on these compounds were subsequently discerned. Based on this analysis, topical agents containing camphor and menthol are potentially effective at treating pain, upper respiratory infection symptoms, and pruritus in addition to potentially functioning as an antimicrobial. However, with a limited number of studies addressing these compounds' uses in each application, no definitive recommendation can be made regarding their use. Given the promising results of earlier studies, the authors recommend that more primary research, particularly randomized, double-blind controlled studies, be done regarding clinical applications of these substances.