The awful truth about oral hygiene and the ills it treats - a dentist speaks out

The smell is caused by bacteria inside the mouth depriving it of oxygen and creating sulphur gas. She advised scratching the tongue with a spoon to verify if it was smelly or not.

Nopmanee warned, however, that frequent use of mouth antiseptic over a prolonged period might lead to distorted taste buds. She said the antiseptic normally simply killed off bacteria for a short period of time and while some suffered from actual bad breath, there were also people who thought they had a smelly mouth but in fact did not. Others again, she said, have received dental treatment but persist in believing they have mouth odour.

She advised brushing properly, including the tongue, and the use of dental floss. She said there was no medical proof that any toothpaste could effectively reduce or eliminate bad oral odour.