Alcohol-free mouthwashes: alcohol is not the active agent, it is the solvent

Patients perceive the alcohol in mouthwash as the element that disinfects, because of the sting it produces. It is a mistaken perception that steers purchasing in the wrong direction.

Alcohol in these formulations acts as a solvent: it keeps the active agents in solution, particularly the essential oils, which do not dissolve in water.

It also acts as a preservative and contributes to product stability. What it does not do, at the concentrations present in mouthwashes, is act as the principal antiseptic.

The stinging sensation is therefore a side effect mistaken for efficacy, and patients tend to read an alcohol-free formulation as weaker when it is not.

The most relevant effect of alcohol is mucosal dehydration. Repeated use reduces lubrication and increases the sensation of dryness, an effect that accumulates over time.

This contraindicates it precisely in the patients who would use mouthwash most willingly: those with xerostomia, where the product worsens the very condition it should offset.

The other contraindications are clear. Patients in treatment for alcohol dependence must avoid it, and some formulations contain high percentages that make the recommendation more than theoretical.

In children it is inadvisable because of the risk of accidental swallowing, which is why paediatric products are all alcohol-free.

Patients with mucositis, ulcers, lichen planus or fragile mucosa report intense pain, and in those conditions alcohol may delay re-epithelialisation.

Alcohol-free formulations use other solvents, typically propylene glycol or poloxamers, and maintain the same concentration of active agent. Documented efficacy is comparable.

Comparison should be made on the declared concentration of active agents, not on the presence or absence of alcohol. Two products from the same brand with the same essential oil concentration have similar efficacy.

The question of oncological risk associated with alcohol in mouthwashes has been raised in the literature without reaching a shared conclusion. It need not be resolved to prefer an alcohol-free formulation, however, given that the benefits are equivalent.

In summary: alcohol is a solvent and not the active agent, stinging is no measure of efficacy, the dryness it induces contraindicates it precisely in xerostomic patients, and at equal active concentration efficacy is comparable.