Peppermint oil (Mentha × piperita) is supported by scientific evidence for the treatment of tension-type headaches, particularly when used topically as a 10% solution in ethanol. Clinical studies have shown that application of peppermint oil to the forehead and temples can significantly reduce headache intensity. The proposed mechanism involves menthol, the main active component in peppermint oil, which produces a cooling sensation, relaxes the underlying muscles, and may modulate pain through effects on the trigeminal nerve. Several randomized controlled trials, including double-blind studies, have found peppermint oil to be as effective as acetaminophen (paracetamol) for tension-type headaches, with fewer side effects. The effect is generally observed within 15–30 minutes of application and can last several hours. Notably, the supporting evidence is specific to topical use; oral use of peppermint essence for headaches is not well supported and may pose risks.

The evidence rating is 3 out of 5 because, while there are multiple positive clinical trials and a plausible mechanism of action, the total number of studies is relatively small, most have been conducted by a limited number of research groups, and long-term safety data are limited. However, peppermint oil is endorsed by some headache specialists and is included in treatment guidelines for tension-type headaches in certain countries.