Dentists discuss the effects of leaving toothpaste uncapped.

Why You Should Always Put the Cap Back on Your Toothpaste

It’s More Than Just a Pet Peeve

In a relationship, couples have their likes and dislikes—and their pet peeves. At the top of many people’s lists is how the bathroom is kept, specifically whether the cap is put back on the toothpaste after using it. It’s simple enough to replace the cap after you brush those pearly whites, but it’s also easy to set the toothpaste down and forget about it when you’re done.

If the latter sounds like you, you’ll want to reconsider your habit. Beyond just annoying your partner, dentists say it can impact your dental health. Read on to find out what really happens if you leave the cap off of your toothpaste.

Bacteria Breeding Ground

If you have a laissez-faire attitude about the toothpaste cap debate, one key fact may sway you. When your toothpaste tube is left open, it’s a “breeding ground for bacteria,” Bill Dorfman, DDS, celebrity cosmetic dentist, says.

“Generally speaking, exposed toothpaste, without the cap on or with a loose cap, can attract germs,” Lauren Becker, DDS at Lauren Becker Dentistry, explains. “This can impact your overall health and well-being. For example, if you leave the cap off in your bathroom, the bacteria that sprays when you flush the toilet could get in it.”

Grossed out yet? It gets worse. According to Dorfman, both bacteria and fungi have been found to grow in toothpaste that’s been left open, as they thrive “in a warm, moist environment.”

Drying Out and Losing Effectiveness

Dentists also say that leaving your toothpaste tube uncapped can cause it to dry out—and nobody likes the feeling of hard, gummy paste on their teeth.

“When you leave the cap off of your toothpaste, it can cause the toothpaste to dry up, making it harder to use,” Jeffrey Sulitzer, DMD, chief clinical officer of SmileDirectClub, tells Best Life.

Beyond drying out, leaving the cap off also means toothpaste can’t really do its job.

Lior Tamir, DDS, general and cosmetic dentist based in San Francisco, explains that when the cap is left off, toothpaste dries out and oxidizes.

“This could make the active ingredients less effective,” Tamir warns. “Essentially, this makes the toothpaste less effective in removing plaque and restoring and remineralizing teeth to reduce cavities.”

Dorfman notes that this is particularly important if you buy toothpaste that contains fluoride.

“Fluoride can break down when exposed to air, light, or heat, leaving your toothpaste unable to protect the teeth against cavities and other oral health problems,” he says. “If an active ingredient like fluoride becomes ineffective, then your toothpaste can no longer protect your teeth, and you run the risk of decay and other oral health problems, which can lead to overall health issues.”

The Consensus

Dentists have a consensus to end the toothpaste cap debate: You should put it back on. In addition, Tamir recommends keeping tabs on the expiration date—”ensuring that you have fresh toothpaste with active ingredients that can keep your teeth healthy, cavity-free, and fresh.”

But beyond preserving your dental health, Becker says changing your ways can positively affect your love life.

“We all know there can be quite a bit of tension at home if one partner is a cap-off type of person and the other is a cap-on type,” she says. “Make sure to talk that out with your partner rather than your dentist.”

On top of this, with prices at the grocery store sky high, we’re all trying to save where we can, which is just another reason to put the cap back on.

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