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

希臘人藉著嚼芳香樹脂與之對抗，而中國人則是使用蛋殼。

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

在古老的猶太法典中，它甚至被視為合法離婚的理由。

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

這個可怕的災禍就是呼出的臭氣，也就是口臭。

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

但造成口臭的原因是什麼，以及為何大家都害怕它呢？

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

想像一下一些不好聞的氣味，例如垃圾、排泄物或是腐敗的肉。

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.

這些味道都與微生物——尤其是細菌的活動有關，此外，就跟聽起來一樣噁心的是，類似的細菌就住在濕氣重的口腔中。

Don't panic.

別緊張。

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.

體內有細菌是很正常的，事實上，細菌在各個方面都是很重要的，例如消化跟預防疾病。

But like all living things, bacteria need to eat.

然而就跟其他生物一樣，細菌也需要食物。

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

口腔中的細菌以黏液、食物殘渣和壞死的組織細胞為食。

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

為了使營養通過細胞膜，它們必須將物質分解成更小的分子。

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

舉例來說，它們必須將蛋白質分解成氨基酸，然後再將氨基酸繼續分解成各種複合物。

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.

惡臭就是這些分解動作導致的副產品，如硫化氫和屍胺，散發在空氣中然後飄到無預警的鼻子前。

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.

我們感覺到這些氣味並將它們解讀成臭味的原因或許是演化機制在警告我們，注意壞掉的食物還有疾病的發生。

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

嗅覺是我們最親密和主要的感覺之一，在吸引伴侶上扮演很重要的角色。

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.

根據調查，59% 的男人和 70% 的女人表示不會跟有口臭的人約會，這可能就是美國人每年花十億美元在各種口腔清潔產品上的原因。

Fortunately, most bad breath is easily treated.

幸運的是，大部份的口臭是很容易治療的。

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.

最難聞的味道來自存在牙齦與牙齒間，以及在舌頭的後方的革蘭氏陰性菌。

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.

用牙刷及牙線清潔牙齒、在睡前使用抗菌漱口水、用塑膠刮刀輕輕地清理舌頭後方，或是選擇吃一頓健康的早餐，就可以消滅大多數的細菌和他們的食物。

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.

但有時候，因為牙齒問題、鼻子狀況或是特殊疾病如肝病和未受控制的糖尿病，這些方法可能不足以解決口臭的問題。

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

如抽菸和過量地喝酒等行為，也有可能導致明顯的臭味。

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

無論原因為何，臭味幾乎都是源自於口腔中，而不是胃或是身體其他部位。

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

但最大的挑戰之一是——在第一時間找出自己口腔的味道，但這為何很困難還不清楚。

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

很可能是因為我們早已習慣自己口中的味道，所以難以判斷自己是不是有口臭。

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

所以像是用雙手摀住嘴巴，或是在手腕舔一口再聞聞看有沒有味道，這些方法其實是沒有用的。

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.

一項研究顯示，即便這麼做人們仍會主觀評價這個味道，依照自己認為這味道多有糟去評斷。

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.

其實有一個簡單但在社交上有點困難的方法：就是深深吐一口氣，然後問問看你的朋友。