Swimmer's Mouth: Pool Water & Your Child's Teeth

Your child hauls themselves out of the pool after another happy afternoon — goggles fogged, fingers pruney, grin enormous. Could all those hours in the water be quietly affecting their teeth?

Here in Marin, summer means swim season. Between the Novato Riptide, the Marin Swim League's ten youth teams (ages 5 to 18), and open swim at spots like the Hamilton Community Pool and the Miwok Aquatic Center, a lot of local kids are logging serious hours in chlorinated water. Swimming is wonderful for growing bodies, and I'd never talk a family out of it. But there's a little-known phenomenon worth knowing about — sometimes called "swimmer's mouth" — so you can protect those smiles while your kids enjoy every splash.

How pool water affects enamel

To stay clean and safe, pools are chlorinated, and that chlorine can make the water slightly acidic. A well-maintained pool is kept in a healthy range — a pH of about 7.2 to 7.6. When a pool drifts too acidic (below 7.2), the water can slowly wear away enamel, the hard, protective outer layer of the tooth.

Here's the mechanism in plain terms: enamel is mostly mineral, and acid dissolves minerals. Normally your child's saliva neutralizes everyday acids and even helps replace lost minerals throughout the day. But when teeth spend hours bathed in acidic water, saliva can't keep up, and the enamel gradually softens and erodes. Enamel doesn't grow back, so this kind of erosion — the slow chemical loss of that outer layer — is something we'd much rather prevent than treat.

The more they swim, the more it matters

How big is the risk? In a CDC study of about 740 swimmers, roughly 15% of those who swam daily showed signs of enamel erosion, compared with only about 3% of people who swam rarely. The pattern is clear: the more time in the water, the higher the risk.

That's why competitive swimmers — the kids practicing six or more hours a week — are the group I watch most closely. In one striking case report, a competitive swimmer developed significant enamel erosion after just 27 days of practice in a poorly balanced, over-chlorinated pool. That's the exception, not the rule, and it took unusually acidic water to do it — but it's a good reminder that pool chemistry matters, and that frequent swimmers deserve a closer look.

What about that brown staining?

Frequent swimmers sometimes develop a yellowish-brown buildup on their teeth, occasionally nicknamed "swimmer's calculus." It forms when minerals and proteins in saliva react with pool water and harden onto the enamel. The good news: it's harmless, and we can remove it with a professional cleaning — included with every Poppy Kids membership visit. For kids who swim a lot, this buildup can return faster, so a few extra cleanings across a heavy training season may be worth it. Either way it's purely cosmetic — not a cavity — so there's no need to worry.

A quick tip: read the ladder

You can often spot a too-acidic pool without any testing kit. If the metal ladders, rails, or fittings look corroded or pitted, the water chemistry may be off — a good thing to flag to whoever maintains the pool.

Simple ways to protect your swimmer

The best news is that prevention is easy and fits right into your summer routine:

How we can help at Poppy Kids

At a regular checkup, I can do what a home routine can't: gently check for the earliest signs of enamel softening before they become a problem, polish away any swimmer's staining, and talk through your child's specific habits. For kids who swim a lot, the American Academy of Pediatric Dentistry (AAPD) supports professional fluoride for those at higher risk, so I may apply a quick fluoride varnish — a painless brush-on coating that helps remineralize and protect enamel through the busy swim months.

So please — keep swimming. The pool is one of the best parts of a Marin summer, and a few easy habits keep your child's smile every bit as bright as their tan. For guidance specific to your child, check with your pediatrician and me — and feel free to reach out to schedule a summer checkup before the season really heats up.

— Dr. Andrea