When it comes to our five senses most people think sight and sound are the most important. But smell plays a crucial role in how we interact with our environment, make everyday decisions, build relationships, find mates, avoid dangers, build important memories and prevent disease.
It’s also the oldest, allowing us to detect molecules that can harm or help us. Smell is a powerful sensation. One that can immediately send us back to an event in our past. The moment we detect a smell the olfactory neurons in the upper part of the brain generate an impulse in the olfactory nerve that’s transmitted to the olfactory bulb in the brain. Information about this smell then gets disseminated to the surrounding limbic system- a set of structures that play a major role in controlling memory, behaviors and emotions.
There are several interfaces between the areas of the brain where we sense pain, the hypothalamus and mediodorsal thalamus, and the olfactory and limbic system. In multiple studies, exposure to certain smells increased pain thresholds and helped to manage chronic pain levels. In one study, those exposed to lavender prior to receiving a noxious stimuli all reported a reduced perception of pain, leading the authors to conclude:
- Smell can alter brain activity in the amygdala-one of two clusters of nuclei sitting in each hemisphere in the limbic system. It plays a key role in how animals assess and respond to threats and challenges by evaluating the emotional importance of sensory information and promoting appropriate response. It’s involved in tying emotional meaning to our memories. This suggests smell changes the perception of pain by modulating our emotional response to it.
- It affects breathing patterns. Deep inspiration through the nose allows odors to travel to the olfactory nerve and activate the olfactory cells in the limbic system which, depending on the scent, can unconsciously affect breathing patterns. Calming odors like lavender encourage deep, restful breathing. Those associated with fear, the opposite.
- Research shows the lungs also have odor receptors. Nasal receptors are located in nerve cells but the receptors in our lungs reside in neuroendocrine cells. Instead of sending nerve impulses to the brain they trigger neurotransmitters and neuropeptides when activated and induce construction and coughing to rid the body of noxious fumes.
Aromatherapy has been well documented to modulate stress reactions by quickly inducing physical relaxation as well as decreasing activation of the sympathetic nervous system. In one study, participants who inhaled blended essential oil treatments with sandalwood and lavender for 15 minutes after exercising enhanced their parasympathetic activity. They all showed significant reduction in their heart rates and reported baseline stress levels.
In other studies patients who received massages with lavender oils twice a week for five weeks experienced a 50% reduction in pain. Certain scents activate odor receptors in the nose that then sets off a chain reaction in the central nervous system that ultimately stimulates areas of the brain that controls emotions, releasing “feel good” hormones such as dopamine. The combination of lavender, eucalyptus and rosemary improved mood and decreased pain in another study. Aromatherapy is effective because it works directly on the amygdala so the conscious side of our brain can’t diminished or inhibit the effects because it’s felt the instant the scent is inhaled. Thinking can’t alter its immediate impact on the emotional centers in our brains.
Another benefit is a better nights sleep. We already know cutting out all light or putting on ocean waves can be the ticket to dreamland. But adding your sense of smell can be just as effective. Inhaling or applying essential oils to the skin can be a wonderful resource. In one study researchers found that lavender increased the amount of slow and deep wave sleep in participants, with everyone reporting feeling invigorated the following morning.
The vagus nerve system acts to counterbalance the fight or flight system and can trigger a relaxation response in our body. New studies have shown it’s the all-important gearshift. In fight or flight mode, digestion is shut down, clearly the last thing we require to survive. But when in a perpetual state of stress, digestion stagnates and IBS, GERD, and constipation can occur, allowing toxins and waste to accumulate. Stimulating the vagus nerve can end this state and restart gastric motility by activating saliva in the mouth, acids in the stomach, pancreatic enzymes and gallbladder bile excretions necessary to breakdown food and insure absorption of all the nutrients we consume. A blend of clove and lime has been shown to achieve this goal.
But not all scents are created equal. Individual and blended scents can activate different bodily responses.
In one study lavender was the most effective fragrance in producing calming affects by increasing blood flow and decreasing heart rate, blood pressure and galvanic skin conductivity- a physiological indication of decreased sympathetic activity. Whereas rosemary decreased blood flow but increased systolic blood pressure immediately after inhalation because both the sympathetic and parasympathetic systems were activated. This dual impact increased alertness and reduced cortisol levels know to increase stress. Mint increased alertness and performance. It is a great addition to tea or coffee when late afternoon drowsiness hits.
Aromatherapy won’t stop chronic pain conditions from hurting but they can have a powerful impact on how we feel that pain. Certain fragrances trigger receptors in the nose that then send signals through the central nervous system to the part of our brains that controls emotion. Ultimately feel good hormones are released that elevate our mood and lessens pain. Whether it’s by inhalation or skin contact, adding aromatherapy can enhance anyone’s therapeutic regimen.
Next week I’ll talk about which scents, combinations and treatments have been shown to provide the best responses.