Sweet dreams are made of nice smells - but catching a whiff of something stinky can lead to nightmares, researchers say.
Experts have discovered that when a sleeping person smells something pleasant, such as roses, they have "positive" dreams. But if a person smells an unpleasant odour, like rotting eggs, they tend to have "negative" dreams.
A team of German researchers linked nice smells to sweet dreams after analysing 15 sleeping women over a month-long series of tests.
Over the course of the month, the researchers released various "volatile" odours near the sleeping women. When they were awoken, the women were asked to describe their dreams.
The researchers said releasing pleasant odors around someone who was asleep could be "therapeutic".
“The emotional coloration of dreams can be significantly influenced in accordance with the hedonic aspect of the stimulant," the researchers said.