This Livestrong article - Does Parsley Help With Bad Breath? suggests that parsley can improve bad breath.
The article suggests that bad breath is caused often by poor oral hygiene, allowing bacteria to metabolise food particles and produce sulphur compounds which smell bad. This is the established scientific status-quo, however it does not mention that parsley has any antibacterial properties. The benefits are claimed to be due to chlorophyll and I quote:
This substance has antioxidant and anti-inflammatory properties and helps to neutralize toxins and pollutants you ingest daily.
However, some bad breath tablets contain parsley seed oil suggesting it isn't universally believed to be the chlorophyll that helps.
Does anyone know of any research to support this?