Essential Science: Bug Off!

Don't let the bugs bug you this spring. 

By Jeff Dorsett, MSHS


Game On

As we leave winter behind us and approach spring, many of us are yearning to get outdoors, to breathe fresh air, and to once again feel the warmth of the sun. For the more sports-minded, spring is a perfect time for getting back to shooting some hoops, working on your pass, or hitting the green. Yes, spring has something to offer all of us. Spring is also a time when mosquitoes and other insects begin to feed. As the swarms descend, we scurry to our cabinets or first aid kits to find the long forgotten, often synthetic, chemical-based repellents, in hopes of warding off the feeding frenzy. However, there are several safety concerns related to both environmental and human health, with the use of synthetic chemicals to control insects and other pests.1 Therefore, now is a good time to brush up on the benefits of essential oils and their repelling properties. Just like preparing for a sport or other outdoor activity, protecting oneself from pests requires knowledge and planning.

The Best Offense Is a Good Defense

Arguably, no defense is better than Mother Nature’s offerings. Nature has granted every living organism unique abilities and mechanisms to fight for its continued survival.1 For example, to ensure our continued survival, humans have the ability to run, hide, or fight when presented with an immediate threat. Had we lacked these basic abilities throughout history, our species would have ceased to exist. The same is true for other mobile creatures. But what about nature’s less mobile inhabitants (e.g. plants) that lack such defensive mobility? How have they survived for millennia without these abilities?

Hang Time

For centuries, these same essential oils have been traditionally used by native human populations throughout the world to ward off mosquitos and other insects.1 In fact, the hanging of repellent plants throughout the home, after bruising them to release the essential oils, is still a common practice in developing countries.2 Modern scientific research has validated the traditional use of essential oils as natural repellents. Many essential oils extracted from various plants have been shown to have excellent repellency properties.3 Generally, the unique combination of monoterpenes and sesquiterpenes found in these oils may contribute to their repellent properties.1 Alpha-pinene, cineole, eugenol, limonene, terpinolene, citronellol, citronellal, camphor, thymol, and beta-caryophyllene are commonly found in essential oils that have the ability to repel mosquitoes.3–7

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Working as a Team

The term “synergy,” in the context of essential oils, means that often increased activity is found in the use of the whole oil rather than just one of its constituent parts. The same can be said of blends of essential oils having greater activity than that of any one of the single essential oils that make up the blend. It is easy to attribute repellency activity of an essential oil to one or two compounds; however, there is scientific support for a potential synergistic repellent effect among the various components.3, 7, 8 In fact, several studies have demonstrated that pure isolated compounds are less effective repellents than that of the essential oil in which they are found.1–3 It is believed the minor constituents found in essential oils act synergistically with the major constituents, improving the overall efficacy.3 This concept of synergy is key when developing natural, essential-oil-based repellents; a product based on a mixture of whole essential oils is often more powerful than one based only on one oil or component.

Mother Nature’s Playbook

Drawing upon Mother Nature’s blueprint, scientists have developed insect repellent formulations (e.g. sprays, creams, gels, and lotions) based on the unique protection afforded by plant-based essential oils. Many essential oils (including Arborvitae, Cedar, Cinnamon, Citronella, Clove, Geranium, Lemongrass, Spearmint, Peppermint, Rosemary and Thyme) have known repellency properties, and are considered safe for repelling insects, when used appropriately.9 In choosing an essential-oil-based repellent, look for one that contains one or more of these essential oils or that share similar chemistry. Also, essential-oil-based repellents tend to lose efficacy relatively quickly-they are volatile, aromatic compounds after all. So it is important that the formula should contain a fixative ingredient, like Fractionated Coconut Oil10 to help keep the essential oil on the skin longer and thus help increase repellent efficiency. Vanilla absolute, which contains vanillin, is also a great addition to any essential-oil-based repellent, because it can also prolong efficacy.1–3

This year, as you go outside and enjoy all that Mother Nature has to offer, don’t let the bugs bug you. With a little pre-game planning, you can ensure that you have a great outdoor experience.

The Game Plan

  1. Common “scents” defense. Use a good essential-oil-based repellent that contains a blend of two or more essential oils with known repellency properties (see list above). Blends containing Cedar essential oil are particularly useful and provide an aroma profile that is reminiscent of nature. Additionally, the product should contain a fixative like Fractionated Coconut Oil and/or vanilla absolute, to help ensure long-lasting efficacy.
     
  2. Dress for the occasion. Weather permitting, wear long sleeve shirts, pants, and socks to provide a first-line physical barrier.

  3. Keep your eye on the clock. Mosquitoes are generally most active between the hours of dusk and dawn, so plan your day accordingly.

References

1. J. U. Rehman, A. Ali, and I. A. Khan, “Plant based products: use and development as repellents against mosquitoes: A review,” Fitoterapia, vol. 95, pp. 65–74, Jun. 2014.

2. M. F. Maia and S. J. Moore, “Plant-based insect repellents: a review of their efficacy, development and testing,” Malar. J., vol. 10, no. Suppl 1, p. S11, Mar. 2011.

3. L. S. Nerio, J. Olivero-Verbel, and E. Stashenko, “Repellent activity of essential oils: a review,” Bioresour. Technol., vol. 101, no. 1, pp. 372–378, Jan. 2010.

4. T. G. T. Jaenson, K. Pålsson, and A.-K. Borg-Karlson, “Evaluation of extracts and oils of mosquito (Diptera: Culicidae) repellent plants from Sweden and Guinea-Bissau,” J. Med. Entomol., vol. 43, no. 1, pp. 113–119, Jan. 2006.

5. B.-S. Park, W.-S. Choi, J.-H. Kim, K.-H. Kim, and S.-E. Lee, “Monoterpenes from thyme (Thymus vulgaris) as potential mosquito repellents,” J. Am. Mosq. Control Assoc., vol. 21, no. 1, pp. 80–83, Mar. 2005.

6. Y.-C. Yang, E.-H. Lee, H.-S. Lee, D.-K. Lee, and Y.-J. Ahn, “Repellency of aromatic medicinal plant extracts and a steam distillate to Aedes aegypti,” J. Am. Mosq. Control Assoc., vol. 20, no. 2, pp. 146–149, Jun. 2004.

7. Y. G. Gillij, R. M. Gleiser, and J. A. Zygadlo, “Mosquito repellent activity of essential oils of aromatic plants growing in Argentina,” Bioresour. Technol., vol. 99, no. 7, pp. 2507–2515, May 2008.

8. L. A. Hummelbrunner and M. B. Isman, “Acute, sublethal, antifeedant, and synergistic effects of monoterpenoid essential oil compounds on the tobacco cutworm, Spodoptera litura (Lep., Noctuidae),” J. Agric. Food Chem., vol. 49, no. 2, pp. 715–720, Feb. 2001.

9. O. US EPA, “Active Ingredients Allowed in Minimum Risk Pesticide Products.” [Online]. Available: http://www.epa.gov/minimum-risk-pesticides/active-ingredients-allowed-minimum-risk-pesticide-products. [Accessed: 11-Dec-2015].

10. N. G. Das, D. R. Nath, I. Baruah, P. K. Talukdar, and S. C. Das, “Field evaluation of herbal mosquito repellents,” J. Commun. Dis., vol. 31, no. 4, pp. 241–245, Dec. 1999.

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