That nasty stench just won’t go away.

You’ve brushed and flossed until your gums bleed, swished mouthwash until it stings.

But your breath still reeks of last night’s meatloaf or this morning’s maple syrup oatmeal.

Even if you think you’ve taken all the precautions, dentist Paul Herrera of the Lawrence Dental Center says you might be missing something.

“Certain bacteria cause bad breath,” he says.

So what’s the secret to a minty fresh breath that lasts all day long, you ask. The answer might surprise you.

“First and foremost, the main cause of bad breath in a healthy person is bacteria on the tongue,” Herrera says.

Research has shown the most common bad breath-causing bacteria are located on the posterior portion of the human tongue.

Herrera wouldn’t disagree with that notion. He’s seen a lot of tongues in his line of work.

“If you look at your tongue, it should be pink,” he says. “It should not be coated with yellow or white or brown.”

To eliminate buildup on the tongue, Herrera suggests purchasing a tongue cleaner.

“Essentially they are scrapers,” he says. “You can scrape the back of the tongue and get the coating off.”

These tongue cleaners can be purchased at stores such as Wal-Mart, CVS and Walgreens.

Of course, tongue bacteria aren’t the only causes of stinky, smelly breath.

“There are various causes,” Herrera says. “It could be certain kinds of foods they eat.”

Among the most odorous foods to eat are garlic, cheese, fish and onions.

“A good, healthy diet goes a long way,” Herrera says.

Although Herrera says he’s had several clients who have shown concerns about their breath, Brad Grant says it’s less common at a pharmacy.

Grant, a pharmacist at King Pharmacy, 1112 W. Sixth St., says if a customer asked him for advice about eliminating bad breath, he’d check into the person’s background.

“I’d want to find out some different things about them as person,” he says, “from a hygiene standpoint.”

Good oral health consists of brushing and flossing your teeth regularly, says Herrera, who also would examine a patient’s hygiene when consulted about the topic.

“That’s all part of good oral health,” Herrera says. “But cleaning the tongue is overlooked by a lot of people.”

People who smoke, for example, should be concerned about having an odorous breath, Herrera says.

“That’s an obvious cause of bad breath,” he says.

If you’ve done everything — brushed, flossed, scraped your tongue, quit smoking, started eating healthier — and you still have bad breath, Herrera says you might have more serious problems.

Some common bad breath-related illnesses are gum disease, heart, liver or kidney problems and even diabetes, according to simplestepdental.com.

“I’d probably look and see if there was some sort of physical condition,” Grant says.

Despite this, Herrera says people shouldn’t worry too much about a serious health problem — the most common cause of bad breath, after all, is merely the scum on your tongue.

“You can address it by cleaning the tongue,” he says. “I just believe that if (bad breath) is an issue, you need to make people aware of all the causes.”