Your daily mouthwash: alcohol, chlorhexidine and a lot of marketing

The daily mouthwash: alcohol, chlorhexidine and plenty of marketing

A dentist tells a patient to stop using Listerine because alcohol isn't good for them. The patient complies, switches to a more expensive pharmacy brand and, along the way, starts wondering whether to alternate a fluoride one with a "natural" one from the herbalist shop because of the fluoride controversy. The scene repeats itself in thousands of bathrooms every morning: a lot of money spent and very little idea of what the liquid we spit out actually does.

The first piece of evidence that emerges when you scratch beneath the surface is that mouthwash is, for several participants in the debate, dispensable. Brushing and dental floss or interdental brushes do the job; mouthwash is a complement, not the foundation. And if you use it daily, better alcohol-free: some warn of burning, dryness and, with sustained use, a higher risk of lesions in the oral lining, although others defend its daily use without problems.

What's behind "alcohol-free" and the pharmacy price

The dentist's argument isn't a whim. According to links shared in the debate, mouthwashes with alcohol concentrations above 10% can cause stinging and damage in the mouth, and systematic use is associated with damage to the oral lining. That doesn't make Listerine poison, but it does explain why some professionals have stopped recommending it as a routine.

The jump to the pharmacy product, on the other hand, is more questionable. Some argue that the 0.12% alcohol-free chlorhexidine from the pharmacy and the supermarket version have the same composition and the same percentage. Paying triple for the white box is, in that view, an act of faith, not of chemistry. Chlorhexidine, however, is the most powerful antiseptic of the family and also the one that stains teeth if used for more than two weeks in a row: it's for specific flare-ups, not for everyday use.

Baking soda, hydrogen peroxide and coconut oil: the low-cost route

Against the pharmacy shelf, one camp defends what's already in the kitchen. Half a glass of water with half a teaspoon of baking soda costs pennies and some back it up with studies. Hydrogen peroxide diluted 50% with tap water is another oft-repeated recipe, with the warning not to overdo it. And virgin coconut oil, with ten minutes of swishing and spitting into the bin to avoid clogging the pipes, is claimed as an alternative to chlorhexidine.

None of these homemade formulas has gone through a serious clinical trial under the conditions in which they're used at home. They work as an economic argument —a kilo of baking soda costs 1.20 euros and lasts more than a year— and as an excuse not to pay for a brand. The problem is that the mouth has beneficial bacterial flora, and disinfecting it bluntly isn't free either.

Fluoride and the "natural" product trap

The idea of alternating a fluoride mouthwash with a fluoride-free one from the herbalist shop sounds like a reasonable balance and is, in fact, a way of doing neither thing properly. Topical fluoride is the tool with the most evidence against cavities; the fluoride-free "natural" one adds nothing that brushing hasn't already done. Alternating for the sake of it is marketing with a clear conscience.

The anecdote that throws people off: someone who has used daily Listerine for years boasts perfect teeth and no cavities. It may be true and prove nothing. There are centenarian smokers too. Genetics, diet and brushing frequency matter more than the colour of the liquid.

In the end, the million-dollar question isn't which mouthwash is best, but why we keep buying one at all.