In serving plant functions, essential oils perform many duties. They regulate plant growth, like hormones. They help in plant metabolism, like enzymes. They also provide the basis for the plant's immune system warding off undesirable viruses, bacteria, microbes, fungi, parasites, and insects. When a plant is cut, it bleeds the oleo-gum-resin into the wound which initiates healing.
Because God created the plants for us (Genesis 1:11-12, 28), their oils can serve many of the same purposes for us as they do in plants. Thus, they can support and balance our endocrine, circulatory, digestive, nervous, and reproductive systems. They can clear our sinuses and lungs to help us breathe better. They can help us metabolize our nutrients, minerals, and vitamins. They can also boost the natural defenses of our immune systems so we can fight off disease by our own abilities. And while they are friendly to us, they can be hostile to bacteria, viruses, parasites, and fungi. In this way they can attack invading offenders directly.
Many oils, applied to the skin, are also effective insect repellents. Cedarwood and myrrh are excellent in this regard, a fact that has been known and applied since ancient times. Citronella was also used as an insect repellent in Biblical times, but is not mentioned in the Bible. A few drops of mint, a Biblical oil, can be mixed with water and sprayed on rose bushes to control aphids.
And just as the bleeding resins of plants fill the wound and initiate the healing process for the plant, pouring of essential oils into cuts and wounds can accelerate healing and protect from infection because of their antiseptic capabilities. Most essential oils are microbicides to some extent. The most gentle Biblical oils are aloes (sandalwood), balm, bay, bdellium, coriander, cedarwood, cumin, cypress, frankincense, galbanum, henna, jupiter, myrrh, onycha, rue, shittim (acacia), and spikenard. The stronger antiseptic Biblical oils include anise, calcmus, cassia, cinnamon, dill, fir, hyssop, mint, mustard seed, pine, terebinth and wormwood.