BAD BREATH

As well as causing stress, bad breath can be exacerbated by stress. It can also be caused by throat and sinus infections or periodontal disease. Breath can also become foul from smoking, drinking alcohol and eating foods such as garlic.

But "bacteria in the mouth is the major cause of bad breath," says Anne Bosy, clinical and research director of the Fresh Breath Clinic in Toronto, Canada. "And some bacteria can cause odour that can be smelled from metre or so away."

Jiahui is troubled by her bad breath. Although she has not refrained from social interactions altogether, she has become particularly sensitive about other people's body language. "When is see someone rubbing his nose, I think it is because of my bad breath," she says. "I feel a bit paranoid and keep a certain distance from others."

All it took was a visit to her dentist to find that she suffers from severe periodontal disease - a chronic bacterial infection that affects the gums and bone supporting the teeth. Now Jiahui carries a toothbrush and toothpaste with her, and takes the time to brush after every meal.

"I've consulted Chinese herbalists. I drink plenty of water, eat simple foods, cut down on spicy and fried food, and get plety of sleep," she says. "When my condition improves I'll feel a little more relaxed."

"It's important to practice good oral hygiene," Bosy says. "But once some bacteria set in, the problem may require antimicrobial mouthwashes, such as those containing zinc - which can alter the metabolism of the bacteria and prevent them from producing suphur, which has distinct odour - or those containing chlorhexdine, which destroys he bacteria."