To elude these problems, investigators are exploiting alternative therapeutic strategies, such as the use of natural products. Among new therapeutic approaches based on medicinal plants and their extracts, the use of essential oils is increasingly under investigation. Interest in essential oils has revived in recent decades with the popularity of aromatherapy, a branch of alternative medicine that claims that essential oils and other aromatic compounds have curative properties, in elderly too. For example, lavender essential oil is used to ease anxiety and nervousness, and it has been shown to improve balance in older adults. Essential oils are concentrated hydrophobic liquids containing volatile aroma compounds of plant secondary metabolism, obtained by distillation. Essential oils have a wide application in folk medicine, fragrance industries, as well as food flavouring and preservation, but only in recent years, they have started to be recognized for their potential antimicrobial role.
This new trend is due to the increasing spread of microorganisms resistant to conventional antimicrobial agents. Essential oils, containing hundreds of naturally active ingredients in variable proportion, eliminate the risk of antibiotic resistance, since microbes are not able to adapt to their heterogeneous structure. For this reason, today, the essential oils are also tested to assess their possible clinical use.
From literature data, although fragmentary and incomplete, there is evidence that essential oils are active against many microorganisms, such as bacteria, fungi, parasites, and viruses, being able to eliminate pathogens while preserving "friendly" microorganisms. Moreover, essential oils do not seem to seriously harm the body, as they do not accumulate in the liver or kidneys, do not cause microbial resistance. Besides, essential oils seem to stimulate the immune system; hence, they could be used both to prevent and to treat microbial infections.
However, these promising experimental microbiological data are often insufficient, as they are not always based on validated methodologies and experimental models with good predictability for clinical use
Although the increased susceptibility of older persons to infectious diseases frequently has been attributed to the decline in immune function that occurs with ageing, there are very few data confirming this hypothesis. Additional research is clearly needed on other contributory factors such as nutrition, ciliary transport, bacterial adherence, neutrophil and macrophage functions, and complement.