**7. Application of essential oils in therapy**

Daily, the human body comes into contact with EOs through various sources such as herbs, spices, orange, spearmint, lemongrass, etc., but only limited information about the amount of EO uptake is known [4, 88]. Effects of EO begin to appear after it penetrates the human body in several ways such as by ingestion, by absorbing the EO or diffusion, and by inhalation [4, 89]. EOs can be taken by inhalation through the lungs and distributed into the blood because of their volatility [90–92]. Moreover, consumption of EO by ingestion should be taken with care because EOs may cause probable toxicity [4]. EOs are used in folk medicine to treat many health problems and can also be used as food preservatives by giving antimicrobial, antioxidant, and anti-inflammation properties [93, 94].

Many studies investigated the efficiency of EOs in combination with antibiotics to combat bacterial resistance; EOs with its compounds and secondary metabolites have shown promising synergistic interaction as an indication that they would be helpful to treat and decrease bacterial resistance to antibiotics [39, 95]. The advantages that make the EOs preferable are that they will decrease adverse reactions, besides being comparatively more cost-effective, with more public acceptance due to traditional usage, and being renewable with better biodegradability properties [39, 96].
