Eucalyptus for Bad Breath

A 2010 study found that a chewing gum containing eucalyptus significantly decreased bad breath, volatile sulfur compounds (a common cause of bad breath), and decreased tongue coating compared to placebo over 12 weeks. Eucalyptus is thought to reduce bacteria that produce volatile sulfur compounds in the mouth.

Tanaka M, Toe M, Nagata H, Ojima M, Kuboniwa M, Shimizu K, Osawa K, Shizukuishi S. Effect of eucalyptus-extract chewing gum on oral malodor: a double-masked, randomized trial. J Periodontol. 2010 Nov;81(11):1564-71. doi: 10.1902/jop.2010.100249. Epub 2010 Jul 1. PMID: 20594055.