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  • There is a curse that has plagued humanity since ancient times.

  • The Greeks fought it by chewing aromatic resins, while the Chinese resorted to egg shells.

  • In the ancient Jewish Talmud, it's even considered legal grounds for divorce.

  • This horrible scourge is halitosis, otherwise known as bad breath.

  • But what causes it, and why is it so universally terrifying?

  • Well, think of some of the worst odors you can imagine, like garbage, feces or rotting meat.

  • All of these smells come from the activity of microorganisms, particularly bacteria, and, as disgusting as it may sound, similar bacteria live in the moisture-rich environment of your mouth.

  • Don't panic.

  • The presence of bacteria in your body is not only normal, it's actually vital for all sorts of things, like digestion and disease prevention.

  • But like all living things, bacteria need to eat.

  • The bacteria in your mouth feed off of mucus, food remnants, and dead tissue cells.

  • In order to absorb nutrients through their cell membranes, they must break down the organic matter into much smaller molecules.

  • For example, they'll break proteins into their component amino acids and then break those down even further into various compounds.

  • Some of the foul-smelling by-products of these reactions, such as hydrogen sulfide and cadaverine, escape into the air and waft their way towards unsuspecting noses.

  • Our sensitivity to these odors and interpretation of them as bad smells maybe an evolutionary mechanism warning us of rotten food and the presence of disease.

  • Smell is one of our most intimate and primal senses, playing a huge role in our attraction to potential mates.

  • In one poll, 59% of men and 70% of women said they wouldn't go on a date with someone who has bad breath, which maybe why Americans alone spend $1 billion a year on various breath products.

  • Fortunately, most bad breath is easily treated.

  • The worst smelling byproducts come from gram-negative bacteria that live in the spaces between gums and teeth and on the back of the tongue.

  • By brushing and flossing our teeth, using antibacterial mouthwash at bedtime, gently cleaning the back of the tongue with a plastic scraper and even just eating a healthy breakfast, we can remove many of these bacteria and their food sources.

  • In some cases, these measures may not be enough due to dental problems, nasal conditions, or rarer ailments, such as liver disease and uncontrolled diabetes.

  • Behaviors like smoking and excessive alcohol consumption also have a very recognizable odor.

  • Regardless of cause, the bad smell almost always originates in the mouth and not the stomach or elsewhere in the body.

  • But one of the biggest challenges lies in actually determining how our breath smells in the first place, and it's unclear why.

  • It maybe that we're too acclimatized to the smell inside our own mouths to judge it.

  • And methods like cupping your hands over your mouth, or licking and smelling your wrist don't work perfectly either.

  • One study showed that even when people do this, they tend to rate the smell subjectively according to how bad they thought it was going to be.

  • But there's one simple, if socially difficult way of finding out how your breath smells: just take a deep breath and ask a friend.

There is a curse that has plagued humanity since ancient times.

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B2 US TED-Ed bacteria breath bad smell smelling

【TED-Ed】What causes bad breath? - Mel Rosenberg

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    稲葉白兎 posted on 2020/11/06
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