Research presented at the 2008 Annual Meeting of the American Academy of Otolaryngogy—Head And Neck Surgery suggests that exposure to odors during sleep impacts the emotional content of our dreams. Pleasant smells make for positive dreaming, while nasty odors turn things nightmarish.

A team of German researchers monitored the brain activity of 15 volunteers while they slept, and used a computer-controlled device to release a pleasant (roses) or unpleasant (rotten eggs) scent while the subjects were dreaming. Then they woke the sleepers and asked them to rate the positive and negative emotional content of their dreams. Exposure to the bad smell led to slightly negative dreams, while the scent of roses yielded moderately positive emotional content (an average of 1.2 on the 0–3 scale that the dreamers used). "The effect is very robust; it had the same tendency in every one," says Dr. Boris A. Stuck, who directed the study. "So we could got statistically significant results even with very few subjects." He and his team are planning larger studies and hope to test the phenomenon as a treatment for nightmares. [Catnaps, dreams can accelerate learning]

If you're looking for sweeter dreams, you could certainly try to replicate this effect yourself. There's one tricky part, though. "Our sense of smell is very rapidly adapting," says Stuck. "If you have a constant stimulus, the smell disappears. So having a constant odor in the room is most likely not the solution." To get around that, we suggest:

• Keep a night-blooming plant nearby, so its aroma will waft over you as its flowers open. "Epiphyllum makes a great houseplant, and it's super easy to grow," says Lisa Gabory, landscaping coordinator at the Rodale Institute Working Tree Center. She also suggests planting mock orange, moonflower, jasmine or sweet autumn clematis outdoors near a bedroom window. Or place fresh cuttings in water in a vase before bed.

• Use fragrant essential oils and a plug-in aromatherapy diffuser. Get one with a timer, or plug it into a timer, so the odor will be released after you're asleep.

If you share a bedroom with someone who retires later than you do, ask your partner to put out some fragrant flowers or essential oil after you've dozed off.

• Avoid using synthetic air fresheners. New research suggests that their chemical fragrances contain carcinogens.

This story is by Rick Chillot and originally appeared on It is reprinted here with permission.

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