## 6 Conclusions  
EOs and their constituents are of growing interest in some fields, especially the food and veterinary industry, but their application in medical settings is still lacking. Given the sheer diversity of EOs, this might be a substantial concern, as they could theoretically be used in treating various conditions. Even the methods whose results are equal to that of an EO alone can have possible medical applications by delivering the EO to a tissue that would otherwise be unreachable without the carrier.  
Despite their low production costs and mucoadhesive and hemostatic properties that can become useful in wound dressings, alginate and cellulose do not have antimicrobial properties on their own, which can limit their effectiveness. Chitosan might prove to be their substitute, but there have been no clinical studies on it so far. PLGA can be another promising alternative to the aforementioned drug delivery systems. It can provide adequate scaffolding for wound dressings and may also deliver various EOs. However, its high production costs and low loading capacity need to be addressed. Other more economical drug delivery systems like zein and nanoemulsions suffer from low water solubility in the case of the former and oxidation potential and low loading capacity in the latter. Nevertheless, zein has been shown to have a high loading capacity, whereas nanoemulsions have been shown to be generally stable. Zeolites are promising due to their possible modification to accommodate various EOs and bactericidal properties; however, they are susceptible to pH changes and water presence. A similar problem is present in the case of the liposomes, which, aside from the mentioned susceptibility, are also unstable and have low loading capacity despite their synergistic effects when loaded with EOs. A summary of the significant advantages and disadvantages of different delivery systems loaded with EOs can be seen in Figure 4.  
The studies we assessed in this review are mostly limited in scope. The discrepancies in methods used can be partially responsible for the differences in results from the in vitro studies. Clinical studies are limited regarding patient numbers and the range of conditions. Hence, it is not easy to make firm conclusions regarding the efficacy and safety of EOs combined with a given drug delivery system. The lack of research in this area seriously hinders the full potential of EO utilization as a possible antimicrobial drug. Nevertheless, this review shows that various drug delivery systems can potentially mitigate the most common problems regarding the EOs.  
Conceptualization, K.H. and P.K.; methodology, K.H. and P.B.; software, P.B.; validation, P.K., M.S., and A.W.; formal analysis, K.H. and M.S.; investigation, K.H.; resources, M.S. and A.W.; data curation, K.H., P.K., and P.B.; writing--original draft preparation, K.H.; writing--review and editing, P.K., M.S., I.W.-K., M.S., and A.W.; visualization, K.H. and P.K.; supervision, P.K.; project administration, P.K.; funding acquisition, M.S. and P.K. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
This article reveals the work of the Student Scientific Circle in the Department of Diagnostic Immunology of the Pomeranian Medical University in Szczecin (Poland).  
Figure 4: Summary of significant advantages and disadvantages of different drug delivery systems loaded with essential oils [72,80].