What are the beneficial effects of peppermint oil?

Relax smooth muscle: Helps with cramps, passing gas. Can increase heartburn (even if enteric coated, but less so), by relaxing lower esophageal sphincter.

A #: Peppermint oil has been used effectively for a variety of digestive issues (flatus, nausea, vomiting, cramps, loose bowel movements, heartburn, indigestion & irritable bowel syndrome). Anecdotally (no scientific proof) it is reported to help with headaches, musculo-skeletal pain, dental pain, upper respiratory infections, inflammatory conditions as well as viral & bacterial infections.