As we all know, there are two sides to every coin. Even though mouthwash can have many positive effects, possible side effects and risks cannot be ruled out.
Increased cancer risk: From a survey of 866 cancer patients and 1249 control participants, a correlation between regular use of mouthwashes and increased cancer risk was found. The more intensive the mouthwash use, the higher the risk. However, in many of the cases with increased cancer risk, tobacco and alcohol use was also recorded, which may have influenced the result (9). For example, a quantitative meta-analysis on this topic also showed no statistically significant association between mouthwash use and cancer risk (10).
Tooth discolouration: Mouthwash can also lead to unsightly tooth discolouration in some cases. Healthy teeth naturally have a slightly yellowish tinge due to strong enamel. Tooth discolouration has a darker tone and may appear irregularly on the teeth. Chlorhexidine is presented as the responsible substance in most studies on tooth discolouration (11).
Dental fluorosis: Because many types of mouthwash contain fluoride, there may be a risk of dental fluorosis. Dental fluorosis manifests itself as white discolouration on the surface of the tooth enamel and is caused by excessive fluoride intake. This side effect is usually only a visual problem, but in the worst case, it can also lead to a loss of tooth substance (12).
Damage to the oral mucosa: Another side effect of mouthwash can be a damaged mucous membrane in the oral cavity. The statistical correlation between the use of mouthwashes and a damaged oral mucosa is quite low. Especially the ingredient sodium has often been mentioned in this context(13).
Impaired taste sensation: Mouthwashes can also change or disturb the sense of taste. This effect could be confirmed clinically, even if only a small proportion of the test persons reported this side effect. The substance chlorhexidine was primarily associated with impaired taste perception (14).