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Dr. Susan Mathison, Published October 26 2011

Mathison: Aromas stir senses

The sense of smell (olfaction) is the most mysterious of the senses. We humans use our sense of smell for many activities, from enjoying the aroma of baking to deciding whom not to sit next to on the bus to initiating escape from a burning building.

The average person can detect the presence of odor molecules at a concentration of less than 1 part in 20 billion, while the average dog smells certain molecules at concentrations of 1 part in 200 trillion.

How does our nose detect odor molecules and transmit that information to our brain?

Every time we inhale, the currents of air carry hundreds of odor molecules up the nose, past the turbinates to the very top of the nasal passages. The surface area covered with special olfactory epithelium is very small, less than the size of a postage stamp. Tiny filaments called cilia within this tissue are the “smell nerves” and are a direct extension of neural tissue, making it the only place where the brain comes in contact with the outside world.

When these nerves are stimulated by odor molecules, the impulse is carried into our brain, perceived and perhaps recognized by the thinking cortex, then passed along the limbic system, which controls emotions and instinctive behavior.

We can distinguish between 10,000 different scents, and only when an odor irritates us, pleases us, or makes us remember something do we pause to take notice. When we first inhale the scents around us, such as smelling pine needles and leaves in a forest, you smell intensely at first. The scent begins to fade as the receptors get used to the scent and stops sending new signals to the brain.

People recall smells with 65 percent accuracy after one year, while the ability to recall photos drops to 50 percent after three months. A familiar scent may elicit strong emotional reactions and trigger powerful memories, whether we’re consciously aware of it or not. In seconds, that message is telegraphed to our central nervous system, which in turn, controls how our body functions and how we feel about those smells.

Like it or not, scent can influence on our appetite, libido, body temperature, heartbeat, stress tolerance, well-being and concentration.

Studies of aromatherapy show that clary sage, an essential oil, stimulate the brain to release a neurochemical that enhances pain control.

Lavender and chamomile triggered the release of serotonin, which minimizes fear, stress and insomnia.

Salty sea air makes us feel refreshed, while wood and spice scents make us feel warm.

Savvy realtors know that the aroma fresh baked bread or cookies increases the likelihood of a fast sale.

Women have long known the power of a signature scent, and may change their perfume based on mood, time of day or activities. Perfumes are described as variable combinations of citrus, floral, green, fruity, herbaceous, musk, woody or oriental.

Scents can be used to manipulate behavior in other ways. A police department from the Netherlands used a barely noticeable orange scent mixed with the standard neutralizing scent in the ventilation system. The effects where astonishing, the inmates where calmer, needed less medicine, showered more. In health care, the a children’s hospital radiology department had a beach theme and used a vanilla spray in the MRI scanner. They noted calmer patients and less need for anesthesia.

Our sense of smell in responsible for about 80 percent of what we taste. Without our sense of smell, our sense of taste is limited to only five distinct sensations: sweet, salty, sour, bitter and the newly discovered “umami” or savory sensation.

All other flavors we experience come from smell. This is why, when our nose is blocked, as by a cold, most foods seem bland or tasteless.

The sense of smell brings us into harmony with nature, warns us of dangers and sharpens our awareness of other people, places and things.

Almost 30 years after he died, I still remember the smell of Grandpa Hans’ pomade. He was a barber for many years in Pelican Rapids, Minn., and all my little brothers sported pomade-slick styles for their first haircuts. The smell of Grandma Daisy’s perfume still lingers, and I still tease my mother about the over-cooked pineapple pudding she forced us to eat decades ago. The smell got to us!

Dr. Susan Mathison founded Catalyst Medical Center in Fargo and created PositivelyBeautiful.com to share her thoughts on beauty, wellness and life.