Toxicity of Mint Oil

Since ancient times, people have extracted oils from peppermint and spearmint plants to treat common ailments like indigestion, headaches and anxiety. However, ingredients in both oils are toxic, and if used incorrectly, these oils can cause serious health problems.

Peppermint Oil

• For some people, peppermint oil can cause rashes and hives when applied directly to the skin. It can also trigger allergic reactions and asthma attacks. According to the American Cancer Society, a study published in the journal "Toxicology Letters" found that large doses of menthone, an organic compound in peppermint oil, caused convulsions and brain damage in laboratory animals.

Spearmint Oil

• Although a splash of spearmint oil can irritate skin and eyes, it is far more toxic if inhaled or swallowed. Vapors from covance, the primary ingredient in spearmint oil, damage mucous membranes and the upper respiratory system. If swallowed, spearmint oil can injure the heart, kidneys and liver.

Menthol

• Menthol is a toxic substance and the primary ingredient in peppermint oil. Spearmint oil also contains menthol but in much lower concentrations. A teaspoon of oil with a high level of menthol can be lethal to a healthy adult. Menthol lowers blood pressure, causes convulsions and spasms, and can induce miscarriages.