Oregano oil P73 causes allergic reactions, reduces the ability of the body to absorb iron and can lead to toxicity, according to Science-Based Medicine. Exposure to the oil also causes irritation to the eyes and the genital region.
When oregano oil P73 causes allergic reactions, it mostly affects people who show allergic reactions to mint, thyme and basil because they belong to the same family, the U.S. National Library of Medicine reports. Due to its carvacrol content, exposure to oregano oil P73 causes irritation to the skin and the eyes.
In 2011, the U.S. Food and Drug Administration reported that oregano oil P73 was a new drug that may not be safe for use by pregnant women. The drug inhibits the body's absorption of iron, which is an essential mineral during pregnancy. Oregano oil P73 contains substantial amounts of carvacrol, cymene, terpinine and thymol. While there is not enough knowledge about the working of oregano, studies conducted on animals show that high levels of carvacrol can cause death, according to Chemcas.com.
Most tests claim that oregano oil has a high ability to kill pathogens based on laboratory tests that use high concentrations of the oil, but Science-Based Medicine reports that it is impossible to reach these high concentrations within the body without increasing toxicity.