Odoriferous Therapy: A Review Identifying Essential Oils against Pathogens of the Respiratory Tract

Abstract

This review explores the body of scientific information available on the antimicrobial properties of essential oils against pathogens responsible for respiratory infections and critically compares this to what is recommended in the Layman's aroma‐therapeutic literature. Essential oils are predominantly indicated for the treatment of respiratory infections caused by bacteria or viruses (total 79.0 %), the efficacy of which has not been confirmed through clinical trials. When used in combination, they are often blended for presumed holistic synergistic effects. Of the essential oils recommended, all show some degree of antioxidant activity, 50.0 % demonstrate anti‐inflammatory effects and 83.3 % of the essential oils showed antihistaminic activity. Of the essential oils reviewed, 43.8 % are considered non‐toxic while the remaining essential oils are considered slightly to moderately toxic (43.7 %) or the toxicity is unknown (12.5 %). Recommendations are made for further research into essential oil combinations.

Choosing the Right Essential Oil for a Mouthwash: Chemical, Antimicrobial and Cytotoxic Studies

“…The essential oils allocated to the third cluster (A3) were the ones that mainly displayed both the highest cytotoxic and antimicrobial effects ( Tables 2 and 3). Interestingly, none of the three oils had any main constituents in common, apart from the mostly inactive monoterpene hydrocarbons that could be brought into connection with the observed cytotoxic and antimicrobial activity [37] …”

“…The majority of the major components were oxygenated monoterpenes with demonstrated antimicrobial effect, known to contribute favorably to the aroma of a mouthwash, such as 1,8‐cineole, menthol, linalool and related derivatives [36] . Other present compounds belonged to sesquiterpenes and phenylpropanoids which have been acclaimed on numerous occasions for their antimicrobial effect or their olfactory agreeable properties [36,37] . Other possibly important contributors included green‐leaf or fatty acid‐derived volatiles, and carotenoid‐derived components.…”

“…Interestingly, none of the three oils had any main constituents in common, apart from the mostly inactive monoterpene hydrocarbons that could be [c] 87 � 8* brought into connection with the observed cytotoxic and antimicrobial activity. [37] Comparing the dissimilarities among the observations in AHC-1 and 2, it appears that the essential oils differ more pronouncedly based on their biological effect than when compared on the basis of their chemical composition. It is not possible to determine a straightforward link between the compositions of the oils and their noted toxicities/activities.…”

“…[36] Other present compounds belonged to sesquiterpenes and phenylpropanoids which have been acclaimed on numerous occasions for their antimicrobial effect or their olfactory agreeable properties. [36,37] Other possibly important contributors included green-leaf or fatty acid-derived volatiles, and carotenoid-derived components. The oils were sufficiently diverse in composition, number and type of functional groups and carbon skeletons of the identified constituents, to allow a correlation of the composition with the observed biological effects.…”

“…It appears difficult to draw a conclusion on the connection between a specific constituent or constituents responsible for the antimicrobial effect and lower cytotoxicity, especially since there is a possible synergistic interaction possible, known for essential oils. [36,37,58]…”