Triclosan, an antibacterial ingredient recently banned by the Food and Drug Administration in some products but currently allowed in toothpaste, appears to accumulate on toothbrushes and can be released in the mouth, according to a study published this week in the journal Environmental Science & Technology.

The FDA began prohibiting the sale of soaps and body washes that contain one or more of 19 antibacterials—including triclosan—last month because manufacturers haven’t proved that they’re safe for long-term daily use and more effective than regular soap and water for controlling certain infections. But because toothpaste is not included in the ban, triclosan can still be found in Colgate Total toothpastes (the only toothpaste line in the U.S. that contains the substance). Triclosan is also permitted in a slew of other items, including cosmetics, athletic clothing, and cleaning products.

Here’s what you should know about triclosan and other substances often used in toothpaste:

What the Study Found

In the new study, University of Massachusetts Amherst researchers tested 22 toothbrushes, mostly manual devices for adults. They simulated three months of twice-a-day brushing, using some toothpastes that contained triclosan and others that did not.

The triclosan, they found, adhered to the nylon toothbrush bristles and to soft rubbery parts such as tongue/cheek cleaners. It remained there while subjects used triclosan-containing toothpaste, and then, when subjects switched to a triclosan-free toothpaste, the chemical found its way back into their mouths from the toothbrush. (The researchers also found that several other chemicals, including butylated hydroxytoluene, or BHT, used as a stabilizer in some whitening toothpastes, behaved similarly.)

The amount of triclosan “freed” in each brushing was highest during the first couple of days after the switch to a non-triclosan toothpaste. It diminished (but didn’t completely dissipate) over a two-week period of observation. “You’re not being exposed to an unusually high dose, but to some you didn’t anticipate,” says Wei Qiu, M.Sc.E., one of the study authors.

Should You Worry About Triclosan?

The health effects of triclosan are still something of an open question. A 2016 review of studies from the University of California San Diego reported that triclosan may contribute to antibiotic resistance and disrupt hormones and immunity; it also has been linked to tumors in mice.

Of course, findings in rodents don’t necessarily apply to people, but, according to Michael Hansen, Ph.D., senior staff scientist at Consumer Reports, “Some studies show adverse effects in mice at dosages consistent with current human levels of exposure.”

In a statement to Consumer Reports, the FDA notes that triclosan in toothpaste has been shown to be effective in reducing plaque and gum inflammation caused by gingivitis, and says, “Based on the scientific evidence, the balance of benefit and risk has been shown to be favorable for this product.” The FDA also says that currently, “medical literature does not change the risk benefit assessment for Colgate Total Toothpaste.”

A 2013 review from the independent Cochrane Collaboration found that toothpaste with triclosan and fluoride reduced plaque and gingivitis more than fluoride-only products.

Colgate Total’s manufacturer, Colgate-Palmolive, said in a statement to Consumer Reports that the study shows the triclosan that might be released is less than the amount a user would get from a single brushing with a triclosan-containing toothpaste. The statement also notes that the Colgate Total line is approved as safe and effective by the FDA.

What should you do? Marvin M. Lipman, M.D., Consumer Reports’ chief medical adviser, says that unless your dentist recommends toothpaste with triclosan, “There’s enough concern now with triclosan safety that it makes sense to avoid it on your own, even if there is some demonstrable value at reducing plaque and gingivitis.”

For gingivitis, our consultants advise that you consider a mouth rinse with stannous fluoride, cetylpyridinium chloride, or the essential oils thymol, menthol, eucalyptol, and methyl salicylate. Your dentist might also recommend a prescription chlorhexidine rinse.

And the study authors, who will be conducting further research on this issue, say consumers who have concerns might consider disposing of toothbrushes when switching from a triclosan-containing toothpaste to one without the substance. Or try an electric toothbrush. As Qui notes, “the bigger the head, the more likely you’ll have chemicals accumulating, and electrics usually have pretty compact heads. We tested one and found less accumulation there.”

What About Other Additives in Toothpaste?

Other ingredients in toothpastes include everything from sweeteners like saccharine to humectants such as glycerol to keep the paste from drying out. When you’re choosing, start with the fundamentals of what an effective toothpaste should contain: fluoride to strengthen enamel (with infants, use just a smear of toothpaste with fluoride when the first tooth pokes out of the gum; between ages 3 and 6, no more than a pea-sized amount of toothpaste is recommended) and a mild abrasive such as calcium carbonate or micronized silica to remove food debris and surface stains.

Other than these, says Jay W. Friedman, D.D.S., M.P.H., a pioneer in the development of quality standards for dental care and a dental adviser to Consumer Reports, opt for a product that bears the ADA Seal of Acceptance, from the American Dental Association. “It tells the consumer that the product, if used as recommended, is not harmful and may offer the benefits as advertised,” he says. Then, he advises, make your choice based on price, the taste that you prefer, and your mouth’s comfort, unless you have problems such as sensitive teeth (see below for more on that). “There isn’t any one best product,” he says. “Find a toothpaste you like that does not cause irritation.”

Beyond the basics, knowing which ingredients work as promised can be challenging. Here, four other types of substances you might find in your toothpaste, the benefits they’re said to deliver, and a reality check on their effectiveness:

Detergents
Toothpaste may contain detergents such as sodium lauryl sulfate and cocamidopropyl betaine. Even though they’re called detergents, they do little to bolster toothpaste cleaning power—they make toothpaste foam up as you brush. Some people who are sensitive to these substances may develop canker sores or experience peeling of mouth tissue after as little as one use.  

If you find that your toothpaste generates more foaming action than you like, use just a dollop on your brush. And if you experience mouth problems like those above, consider nonfoaming toothpastes. (A Google search for nonfoaming toothpaste, SLS-free toothpaste, or toothpaste for canker sores will give you a list of products.)

Whiteners
Whiteners that may be used in toothpaste include hydrogen peroxide, claimed to bleach teeth, and polyphosphates (such as pyrophosphates), said to keep highly pigmented food and drink from staining enamel.

However, in toothpastes, whiteners aren’t concentrated enough or in contact with tooth surfaces long enough to be effective, says Karen A. Baker, M.S., associate professor at the University of Iowa College of Dentistry in Iowa City and an expert on toothpaste ingredients. And polyphosphates may cause canker sores and other mouth lesions.  

Desensitizers
Desensitizers are touted for their ability to relieve the discomfort of sensitive teeth. For example, potassium nitrate reduces tooth nerve sensitivity. Stannous fluoride fills in exposed dentin, keeping food and drinks from stimulating nerves.

Used regularly, desensitizers can ease sensitivity, but our experts recommend seeing a dentist first. “You need to know what’s causing your sensitivity,” says Ruchi Sahota, D.D.S., a spokeswoman for the ADA. For example, untreated gumline cavities, excessive brushing, and aggressive flossing can all lead to sensitivity.

If sensitivity lingers after treatment of a problem like a gumline cavity, or easing up on over-the-top brushing, your dentist might suggest a desensitizing toothpaste, or for persistent discomfort, an in-office treatment such as concentrated fluoride. If that doesn’t help, you might need bonding, a crown, or a root canal to address the underlying cause of sensitivity.  

Xylitol
Xylitol increases saliva production; it’s claimed that this reduces the growth of cavity-causing bacteria in the mouth.

According to a 2015 review from the Cochrane Collaboration, some studies suggested that toothpaste with fluoride and xylitol, a nonsugar sweetener, may be more effective than fluoride-only toothpaste at preventing cavities. But most of the studies were very small and poorly done, and even brushing several times daily won’t deliver enough xylitol to provide a benefit. And if swallowed in large amounts, xylitol can cause bloating, gas, and diarrhea.

Editor's note: The statement from Colgate Palmolive was modified after publication. It originally noted that the study’s authors said they don’t consider oral exposure to triclosan toothpaste to be a health risk. In a followup exchange, however, the study authors told Consumer Reports that assessing the potential health risks of oral exposure to triclosan would require rigorous toxicology studies and is outside the scope of their expertise.