Mouthwashes: what is in them and what each active ingredient actually does

The mouthwash shelf offers dozens of products that look equivalent, and the choice gets made on scent or price because the label does not help distinguish them.

The useful distinction is between cosmetic mouthwashes, which act on breath without altering the biofilm, and therapeutic ones, containing active ingredients with a documented effect on plaque or caries.

The first group masks. The second acts, and it is worth knowing on what.

Chlorhexidine is the most effective against plaque and for that very reason should be used for short periods, as covered elsewhere. It is not a daily mouthwash.

Cetylpyridinium chloride has lower antibacterial activity but better tolerability, and can be used over longer periods. It is the active ingredient in many everyday mouthwashes.

Fluorides have a different objective: they do not reduce plaque but act on enamel remineralisation. A fluoride mouthwash works against caries, not against gingivitis.

Essential oils, typically in combinations of thymol, eucalyptol, menthol and methyl salicylate, have documented efficacy against plaque and gingivitis, lower than chlorhexidine but without its usage limits.

Zinc compounds act on volatile sulphur compounds, and therefore on halitosis, by a mechanism different from antibacterial action.

Hydrogen peroxide at low concentrations appears in whitening products, with limited effect on surface staining.

On alcohol it is worth being precise. Its function is to solubilise the active ingredients and it is not itself the active agent. Alcohol-free formulations exist and are preferable in patients with xerostomia, mucositis, or in treatment for dependency.

The commonest error, however, concerns not the choice of product but its role. A mouthwash does not remove mature biofilm, which is protected by its own matrix.

A mouthwash acts on young biofilm and on already cleaned surfaces. Used in place of brushing it produces no useful result, and this is the piece of information that changes outcomes most.

In summary: cosmetic mouthwashes mask and therapeutic ones act, each active ingredient has a different objective, fluoride is for caries and not gingivitis, alcohol is a solvent and not the active agent, and no mouthwash replaces mechanical removal.