Oregano is an herb of many talents: savory Italian spice, potent antioxidant, bacteria-fighting antiseptic and antiviral. Concentrated oregano oil treats a multitude of conditions including the common flu, insect bites, candida, toothaches, and food poisoning from the microbes E. coli, salmonella and some types of staphylococcus. However, this powerful herbal oil should be limited to low dosages for a maximum of three weeks.
Depletion of Probiotics
In a 1991 study, the International Journal of Food Microbiology reported that oregano oil depletes levels of Lactobacillus plantarum and Leuconostoc mesenteroides, beneficial bacteria that live in the human colon to aid with digestion and protect you from bad bacteria. If you take oregano oil, you might be at risk for gastrointestinal illnesses unless you add a probiotic to your diet. Mayo Clinic nutritionist Katherine Zeratsky, R.D., L.D. recommends probiotic supplements with lactobacillus or other "live and active cultures." Common probiotic supplements include yogurt, miso, soy products and fermented or unfermented milk.
High doses of oregano oil can build toxic levels of thymol in your liver, kidneys or nervous system. Because essential oils are so concentrated, many are toxic in small amounts if taken orally. Limit use to three daily doses for a maximum of three weeks.
Avoid Sensitive Skin
If you use oregano oil topically, steer clear of your eyes, inner nose, genitals and other sensitive mucous membranes. The phenols that make this herb a potent antibiotic also make it too caustic to use full-strength on sensitive areas. Mix it with olive oil, especially if you have a history of skin allergies.
Avoid If Pregnant
Enjoy all the Italian dishes you want, but avoid the essential oil if you're pregnant. High doses can be a uterine stimulant and cause contractions. New moms should also avoid using the oil on their nipples where the baby might ingest it. The infant's immature gastrointestinal system cannot handle thymol oils.