Oregano oil is a potent form of oregano and may possess antibacterial, antifungal and antiseptic properties. Pure oregano oil may be useful in treating certain medical conditions and can be an effective topical treatment. However, oregano oil is not intended for internal use in large doses and topical application may cause side effects. Always contact a doctor with any questions about the proper use of oregano oil.

Lack of Scientific Evidence

According to the Mayo Clinic, while oregano oil has been shown to have antibacterial and antifungal properties, there have not been sufficient scientific studies to prove its effectiveness against certain medical conditions, such as sinusitis. Always speak with a doctor before using oregano oil as a medical treatment.


When placed directly on the skin, oil of oregano may cause an intense warming sensation that may feel similar to a burn. For this reason, oregano oil should not be used on children. Dilution with vegetable oil prior to topical use may reduce or prevent the burning sensation.


Oil of oregano may be toxic when consumed in large doses. Only one drop of oregano oil should be used for internal use and should be combined with olive oil or honey. It can also be added to juice or soy milk.

Questionable Purity

It can be difficult to find pure oregano oil, as many sources are synthetic or have extremely low levels of pure oregano oil. The carvacrol in oregano oil is what provides the health benefits, so look for products with high levels of carvacrol. According to the website Health and Herbs, oregano oil that contains 75 to 85 percent carvacrol and 2 percent thymol is the most effective.