Oregano is one of the strongest antibacterial essential oils. You can smell the oil's power from the first moment the bottle is opened - the aroma is quite intense. According to some aromatherapists, the essential oil may be best used when a strong response to bacterial infection is needed; it has a broad spectrum of bactericidal and anti-microbial action. The oil can kill or halt the growth of a great majority of bacteria.1
The ancient Greeks used oregano to relieve aching and sore muscles and as a poultice to aid in the healing of wounds. The physician Dioscorides references oregano as a remedy for poisonous bites and stings. The Roman herbalist Pliny also cited the use of oregano for poisonous spider bites and it continued to be used for this purpose throughout the Middle Ages. It was also thought to aid digestion, improve eyesight, and ease sea-sickness.2
Oregano oil is non-toxic. The undiluted oil can be irritating and sensitizing to the skin. Do not ingest without first diluting, as it can burn the inside of the mouth. French aroma medical literature advises refraining from long-term use due to possible undesirable changes in liver metabolism.
1 Dadalioǧlu, Itir, and Gulsun Akdemir Evrendilek. “Chemical Compositions and Antibacterial Effects of Essential Oils of Turkish Oregano (Origanum Minutiflorum), Bay Laurel (Laurus Nobilis), Spanish Lavender (Lavandula StoechasL.), and Fennel (Foeniculum Vulgare) on Common Foodborne Pathogens.” Journal of Agricultural and Food Chemistry, vol. 52, no. 26, 2004, pp. 8255–8260., doi:10.1021/jf049033e.
2 Schiller, Carol, and David Schiller. The Aromatherapy Encyclopedia: A Concise Guide to Over 385 Plant Oils. Basic Health Publications, Inc., 2008.
3 Lawless, Julia. The Encyclopedia of Essential Oils: The Complete Guide to the Use of Aromatic Oils in Aromatherapy, Herbalism, Health, and Well Being. Conari Press, 2013.