A lemon-oil gargle for bad breath Original paper

Halitosis (bad breath) is associated with anaerobic mouth bacteria that produce volatile sulfur compounds (VSCs), which are unpleasant-smelling molecules that put the "bad" in "bad breath". In addition to being foul-smelling, VSCs can also cause tissue damage and periodontal disease and can even be transported by the bloodstream to affect other organs.

Treatment for halitosis focuses on reducing the population of these VSC-producing bacteria through a combination of mechanical methods (brushing, mouthwash swishing) and chemical antibacterial agents such as chlorhexidine and cetylpyridinium chloride mouthwashes. However, the commonly used antibacterial mouthwashes aren't always tolerated long-term.

This study examined the effectiveness of a mouthwash formulated with a natural plant extract, lemon peel essential oil (LEO), which was shown to be effective against some VSC-producing bacteria.

In this randomized controlled trial, 48 people with bad breath were randomized into four treatment groups: i) LEO mouthwash (0.56 mg/mL; a concentration previously determined to be ideal in another part of the study), ii) 3% hydrogen peroxide mouthwash, iii) 0.1% cetylpyridinium chloride (CPC) mouthwash, and iv) distilled water (control). The participants gargled with their assigned mouthwash for 3 minutes. At 30, 45 and 60 minutes after gargling, the VSCs in the breath were measured, and saliva samples were collected.

All participants who gargled with a mouthwash, but not the water control, had significantly reduced VSCs at 30 minutes after gargling. Only the participants who used LEO and CPC mouthwashes had significantly lower VSCs after 45 minutes, and only those who used the CPC mouthwash still had lower VSCs after 60 minutes.

The LEO mouthwash also significantly increased salivary pH for nearly 100 minutes after gargling (a higher pH means a less acidic oral environment, which favors dental health), whereas the participants who gargled with CPC mouthwash had significantly lower salivary pH after 1 hour.

The study abstract says that LEO was compared to hydrogen peroxide, CPC, and chlorhexidine mouthwashes, but this seems to be a mistake because no experimental details are listed for chlorhexidine mouthwash.