Unclear or conflicting scientific evidence
- Peppermint
: Peppermint is a flowering plant that grows throughout Europe and North America. Peppermint is most often grown for its fragrant oil. Early research suggests that cleaning the mouth with an essential oil mixture of diluted tea tree, peppermint, and lemon may improve bad breath in intensive care unit patients.
- Avoid if allergic or hypersensitive to peppermint or menthol. Peppermint is generally considered safe in non-allergic adults when taken in small doses. Use cautiously with G6PD deficiency or gallbladder disease. Menthol, a component of peppermint oil, is generally considered safe in non-allergic adults. However, doses of menthol greater than 1 gram per kilogram of body weight may be deadly in humans. Avoid if pregnant or breastfeeding.
- Tea tree oil
: The tea tree (Melaleuca alternifolia) is a small tree with narrow, soft, alternate leaves and yellowish flowers the shape of bottlebrushes. It is one of more than 30 species of paperbark trees that are found throughout Australia. Tea tree oil is obtained by steam distillation of its leaves
and is used in mouthwash for dental and oral health. However, there is currently insufficient evidence in humans to recommend for or against the use of tea tree for bad breath.
- Avoid if allergic to tea tree oil or plants of the Myrtle (Myrtaceae) family, Balsam of Peru, or banzoin. Use cautiously with a history of eczema. Avoid taking tea tree oil by mouth because reports of toxicity have been reported. Avoid if pregnant or breastfeeding.
- zinc
: Zinc formulations have been used since ancient Egyptian times to enhance wound healing. Preliminary research suggests that chewing gum containing zinc may reduce bad breath. The mechanism of action of zinc in reduction of halitosis has not been well reported in the available literature. However, some studies suggest potential anti-bacterial properties of zinc in combination with other ingredients. Additional research is needed before a firm conclusion can be made in this area.
- Zinc is generally considered safe when taken at the recommended dosages. Avoid zinc chloride because studies have not evaluated its safety or effectiveness. While zinc appears safe during pregnancy in amounts lower than the established upper intake level, caution should be used because studies cannot rule out the possibility of harm to the fetus.