A 2016 study published in the European Journal of Dentistry notes that 15 to 20 percent of halitosis cases don’t begin in the mouth. Tonsillitis, acid reflux, diabetes, and even some cancers are among the many conditions that can cause bad breath that defies the most scrupulous oral hygiene.

But as a Healthline article points out, cavities or gum (periodontal) disease are still likely culprits, as both provide places for bacteria to “hide” from a toothbrush or floss. So is dry mouth, which can result from the use of alcohol, tobacco and even certain medications. There are also the usual dietary suspects—here’s looking at you, garlic—whose malodorous effects remain long after they’re consumed. 

The American Dental Association makes several lifestyle and diet recommendations for preventing bad breath. They include brushing twice a day with fluoride toothpaste and flossing once a day; eating a healthy diet (more fruits and veggies and fewer sugary drinks and snacks); getting regular dental checkups; drinking fluoridated water; avoiding tobacco products, and avoiding oral piercings.

Home remedies suggested by Healthline include drinking pineapple juice, eating fennel seeds, and swishing for 30 seconds a day with a baking soda rinse (two teaspoons of baking soda mixed into a cup of warm water). 

Information sourced by Jonathan Richter, DDS, FAGD, owner of Cariodontal, located at 310 E. Shore Rd., Ste. 101, Great Neck, NY (516-282-0310 / Cariodontal.com), and Manhattan Oasis Dentistry, 525 West End Ave., Ste. 1G, New York, NY (212-874-2880 / ManhattanOasisDentistry.com).