London - If something smells a bit unpleasant, it might be because you are feeling anxious, say scientists.

Researchers in the US have discovered that stress can rewire the brain to change the way we perceive smells.

Odours that seemed neutral become unpleasant – and the more stress, the greater the change.

In a study using brain-imaging, volunteers were made anxious by showing them disturbing pictures and text of car crashes and war. This transformed neutral odours to distasteful ones.

Wen Li, a professor of psychology at the University of Wisconsin-Madison, said: “After anxiety induction, neutral smells become clearly negative.

“People experiencing an increase in anxiety show a decrease in the perceived pleasantness of odours. It becomes more negative as anxiety increases.”

“In typical odour processing, it is usually just the olfactory system that gets activated, but when a person becomes anxious, the emotional system becomes part of the olfactory processing stream.”

The study is published in the Journal of Neuroscience. - Daily Mail