When not diluted properly, essential oils have the potential to be dangerous. They can have what’s called “systemic toxicity” leading to cytotoxicity, hepatotoxicity, neurotoxicity, and carcinogenicity. Some essential oils have naturally occurring chemical constituents that, when used or taken in large doses, have the potential to cause or induce cancer. Some of these constituents include safrole, methyl chavicol, and methyl eugenol. This is one of many reasons why proper dilutions are important when using essential oils.