Oregano is an herb that's commonly used in cooking. Oil extracted from its leaves has a long history of medicinal uses.
Over the centuries, it has been used to treat a variety of ailments, including snake and spider bites, respiratory troubles, and menstruation problems. Today, it is marketed for the treatment of a long list of health conditions.
A single study found that taking 200 milligrams of oregano oil three times a day for six weeks eliminated three such parasites. But the study was small, inconclusive, and was funded by a supplement manufacturer.
Some laboratory studies show that oregano or its components have properties that can kill some food-borne germs. But there is no evidence that it helps prevent food poisoning.
Oregano oil has also been used to treat a condition that some alternative medicine practitioners refer to as yeast hypersensitivity syndrome. In this condition, an excess of the yeast candida albicans is thought to cause symptoms, such as sinus congestion, headache, fatigue, and depression. It is not a condition that is recognized by conventional medicine. And there is no evidence that oregano oil helps treat these symptoms.
Oregano oil in an oral or inhaled form is also used to try to treat respiratory tract conditions such as: