The first pair of cranial nerves, also called the olfactory nerves, go directly from the mucous membranes in the top of the nasal cavities to the brain. They give us our sense of smell and also contribute to our perception of taste. In fact, some experts say that smell is as much as 70 percent of what we think of as taste.

So, it should come as no surprise to us that our sense of smell might have a significant effect on other complex processes like nausea and vomiting.

A recent study compared aromatherapy with inhaled isopropyl alcohol (rubbing alcohol) versus oral Zofran (ondansetron) for treating nausea among emergency department patients.

The trial compared inhaled isopropyl alcohol and a 4 mg oral Zofran, inhaled isopropyl alcohol and oral placebo, and inhaled salt water solution placebo and a 4 mg oral Zofran. The primary outcome measurement was nausea reduction from enrollment to 30 minutes after the intervention.

Among emergency department patients with acute nausea and not requiring immediate intravenous access, aromatherapy with or without oral Zofran provides greater nausea relief than oral Zofran alone.

Even though it was a small study, it is nice to have some scientific evidence for aromatherapy with rubbing alcohol. But I have seen people use other smells to try to control symptoms. A recent example was peppermint oil for nausea.

This caused me to wonder about the evidence for essential oils and aromatherapy.

Essential oils probably developed in flowers to attract insects for pollination and in other plant parts as deterrents to predators. All plants contain oils including corn oil, peanut oil and coconut oil. But only about 3,000 contain essential oils, also called “volatile oils” or “aromatic oils,” in their flowers, leaves, bark, wood, fruit or peel.

The term “essential” refers to the essence or fragrance of a plant rather than a necessary component of the oil or something biologically vital. Essential oils are usually extracted by distillation. Whereas, oils produced with the aid of chemical solvents are not considered “true” essential oils.

In theory, chemical components of essential oils may bind to receptors in the smell-sensing part of the brain, affecting the limbic system, which governs emotions and other complex activities.

Essential oils are used in many ways, including application to the skin for possible antibacterial, anti-inflammatory and analgesic effects or to change the odor of cosmetics, perfumes, soaps, detergents, and even insecticides and paints. They are also used in dental products and occasionally as flavoring in medicine and food products. The U.S. Food and Drug Administration (FDA) regulates essential oils in food and pharmaceutical products.

However, essential oils used for aromatherapy do not need FDA approval and cannot legally be promoted to prevent, treat or cure disease. But that does not stop them from being promoted for a variety of conditions, even though the therapeutic effects are not well supported by high quality research.

Some systematic reviews of aromatherapy have been published for nausea and vomiting as well as such conditions as anxiety, dementia, hypertension, pain, sleep and stress.

A review of nine studies regarding postoperative nausea and vomiting included two using peppermint oil and seven using isopropyl alcohol as aromatherapy. They suggested that inhaled isopropyl alcohol was better than placebo but less effective than standard anti-nausea medications. Peppermint oil was not effective.

Another review of five studies about nausea and vomiting concluded that inhaled peppermint or ginger essential oils reduced the incidence and severity of nausea and vomiting and also reduced the need for anti-nausea medications. However, the authors described the evidence as encouraging but not compelling, owing to flaws in the methods used in the research.

It should also be noted that there may be a significant placebo effect of personal expectation for aromatherapy effectiveness, which may play a role in a patient’s responsiveness to treatment. To further confuse things, essential oils are often used with other interventions like massage therapy.

Based on the low frequency of adverse effects reported in the medical literature, the use of essential oils for aromatherapy appears to be safe for most people. But safety in pregnant women or children has not been established. In the limited research available, aromatherapy does not seem to have bad effects on the mother (duration of labor, mode of delivery) or the baby.

So, we still need some large-scale, well-designed, randomized, controlled studies to define the role of aromatherapy in medical care. But I think it is generally OK to try rubbing alcohol and/or peppermint oil for nausea as an addition to (rather than a replacement of) established medical therapy.

Editor’s note: The information in this column is for general information and background only and is not intended for personal diagnosis or treatment. Only your trained medical professional, upon personal examination and appropriate testing, should diagnose your health condition and prescribe treatment.

Dr. Terry Gaff practiced family medicine in Albion for 17 years and is now medical director of the emergency department at Parkview Noble Hospital in Kendallville and the Noble County EMS. Facebook users can become a fan of the Dr. Terry Gaff page at facebook.com/DrTerryGaff, where he focuses on areas of interest and has a little fun in the process. His email address is [email protected] Past columns can be read and comments and questions posted at kpcnews.com/special/health.

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