The research has shown that what people smell while sleeping has a huge impact on their dreams.
This is the first valid study that documents the impact of olfactory function on dreams.
During the study, German researchers used specific volatile odorants with a negative or a positive smell ("rotten eggs" versus "roses") for simulating the participants during sleep.
After the participants woke up, the researchers recorded their impressions.
The team observed that the unpleasant odorant negatively influenced the emotional coloration of the dream, while under stimulation with the pleasant stimulus, nearly all dreams had a positive coloration.
The scientists pointed out that the information on olfactory function during sleep had become available only recently.
The study may also open a potential field of therapeutic intervention with nocturnal olfactory stimulation.
The results of the study were presented at the 2008 American Academy of Otolaryngology - Head and Neck Surgery Foundation (AAO-HNSF) Annual Meeting and OTO EXPO in Chicago, IL.