How to Say "Your Breath Stinks" in Japanese

口が臭い

kuchi ga kusai

口が臭い (kuchi ga kusai) is the Japanese way to say "your breath stinks".

This phrase is used specifically to describe the smell of the mouth or breath itself, rather than a general body odor.

Is there a formal and an informal way to say it?

口が臭い is an informal phrase. Because it is very blunt, it can be perceived as rude or an insult in social settings.

In the phrase 口が臭い, the particle ga marks the mouth as the subject that possesses the quality of being stinky.

kuchi ga kusai

The adjective 臭い (kusai) can also be used metaphorically in slang to mean 'suspicious' or 'fishy', similar to how one might say 'that smells fishy' in English when a situation seems dishonest.
In Japanese culture, the concept of kuuki wo yomu means 'reading the air' to maintain social harmony, which makes telling someone 口が臭い a severe breach of social etiquette.
If you want to be much more polite than saying 口が臭い, you might use the word 口臭 (koushuu), which is the formal noun for 'halitosis'. Using the noun makes the observation sound more like a medical condition than a personal insult.

失礼ですが、お口の中が少し臭っているようです。
Excuse me, but it seems like your mouth has a slight odor.
すみませんが、お口の匂いが強くてちょっと困惑しています。
I'm sorry, but I'm a bit perplexed by the strong odor coming from your mouth.
お口が臭いかもしれないって気づいた？
Have you noticed that your breath might be bad?
友達だから言えるけど、口の匂いがキツいんだよ。
I can say this because we're friends, but your breath is really strong.
口が臭いよ。
kuchi ga kusai yo.
Your breath stinks.
さっきから口が臭い。
sakki kara kuchi ga kusai.
Your breath has been stinking for a while.
本当に口が臭いね。
hontou ni kuchi ga kusai ne.
Your breath really stinks, doesn't it?

A close friend bluntly telling another friend the truth.

健太 Kenta

ねえ、正直に言うけど、口が臭いよ。
nee, shoujiki ni iu kedo, kuchi ga kusai yo.
Hey, to be honest, your breath stinks.
結衣 Yui

えっ、本当に？
e, hontou ni?
What, really?
健太 Kenta

うん、すごく臭いよ。
un, sugoku kusai yo.
Yeah, it stinks a lot.
結衣 Yui

恥ずかしい、ごめんね。
hazukashii, gomen ne.
How embarrassing, I'm sorry.

⭐Share⭐ to appreciate human effort 🙏