Citrus limonum                    Fresh, sharp citrus              Italy

Peppermint oil has shown evidence of helping to control symptoms of Irritable Bowel Syndrome [1].

[1] Grigoleit HG, and Grigoleit P.  Peppermint oil in irritable bowel syndrome.  Phytomedicine: International Journal of Phytotherapy and Phytopharmacology.  2005 Aug;12(8):601-6.