Mouthwash is recommended as part of your oral health routine as it has been shown to be effective at reducing gum inflammation, gingivitis. It is an adjunct, rather than essential for most people. Brushing and flossing, the physical cleaning is more important and more effective.
Mouthwash containing alcohol has not been linked to adverse health effects. Theoretically, it could increase the risk of oral cancer as we know alcohol can do that. However, this is based on studies of consumption of alcohol socially which tends to be over a long period of hours (rather than 2 minutes for mouthwash) and the alcohol is swallowed rather than spat out. As the amounts are so small in using a few ml of mouthwash the risk is thought to be negligible. However, it is recommended to avoid alcohol altogether for pregnant women and of course those with alcohol addiction issues. For those with concerns, the alcohol-free mouthwashes available nowadays are probably just as effective, but we don’t have the same volume of research available to confirm that.
As an everyday mouthwash, Listerine is usually my recommendation as there is a lot of research based on it, seeing as it has been around for many years. For those with active gum problems, I tend to recommend Curasept, but it has side effects (staining, taste) so it is not recommended as an everyday rinse, but only for those having treatment for gu, disease.