Last month I gathered together more information than any usual citizen should sift through and read about mosquitoes, ticks and bug spray. I wanted to better understand how these insects find us, and how well different repellents work and what the safety usage guidelines were for each of them. This is a condensed version of my findings because the whole thing worked out to be 5 pages! If you're interested to know all of it, let me know as it is the basis of my Natural Bug Repellent workshop! To run the course I need a minimum of 6 participants, so if you want more than this teaser, gather your friends!

The Bugs

If it’s not the heat, it’s the bugs that can keep us inside. Mosquitoes, black flies, no-see-ums and ticks can, on their own, be enough to not bother with the walk in the park. What is it about us that makes us so attractive? Besides the itch or sting of some bug bites, why should we worry about protecting ourselves from their presence?

Attraction

Various odours or other chemical markers we produce are what make us trackable by insects. Predominantly, CO2 and ammonia seem to be the most attractive scents on our bodies that mosquitoes and ticks are drawn to. CO2 comes out when we exhale, so the heavier we are breathing, the more volume of CO2 we are expelling. When we sweat, the microflora that live on our skin feed on the sweat and oils our skin secretes. As they feed they produce waste products, one of which is ammonia. Ammonia is part of what makes that glorious stench we know as body odour. And get this, it is particularly that incubated sweat that is the most attractive. It’s not entirely known how this scent tracking works but these problem insects possess structures that pick up these chemical scents in the air and enable the insect to orient itself towards its target. Mosquitoes and ticks have slightly different biting behaviours, but more or less find us the same way.

In Ontario, mosquitoes can carry West Nile Virus, and Black Legged Ticks can carry Lyme disease. Both are capable of carrying other bacterial and viral infections though these two are probably of greatest significance. Thus, efficient protection is worth considering when playing outside.

Need to learn how to ID a tick? Not all ticks are disease vectors for humans, so before you panic should you find one, visit Guelph Tick Tracker and scroll to the bottom.

Protecting yourself

Now that we have that icky stuff out of the way, how do we address repelling these nasties? Considering how they find us, controlling our scent may be number one. Clean clothing that is light and breathable and allows sweat to quickly evaporate will reduce that special mix of ammonia we produce when we sweat. Keeping as cool as possible and considering outdoor exercise choices and locations can be a factor too. For topical chemical control we currently have 2 options available in various forms, DEET containing products and essential oil containing products.

DEET

DEET is probably the most familiar synthetic bug repellent we know, present in the most topical repellents on the market. It is considered safe for responsible human use in maximum concentrations of 30%. Most DEET containing repellents have it at about 23%. Extensive testing has been done on DEET comparing its effectiveness to other repellents as well as its safety for human use. It is considered very repellent for insect landing and biting, and has a long duration of 5-8 hours. Double applications (reapplying in less than an hour) do not increase repellency but rather increase duration. It is absorbed by the skin which is concerning to some people, though it is considered safe for human use. Because of this absorption, many are looking to plant based means of repelling insects. For safe usage guidelines, visit Insect Repellents - Gov't of Canada.

Aromatics

In the lab, essential oils of geranium, citronella, lemongrass, catnip, cloves, lavender, various eucalyptus, basil, rosemary, cedar, peppermint, thyme and likely many others I did not find, have been tested for repellency. And, perhaps with little surprise, they demonstrated very high efficacy with minimal risk to humans given safe use guidelines were followed. Most of the common essential oils are safe for use within reason though some do pose their own risks. EO's like lemongrass can be sensitizers meaning, after repeated exposure, one can develop something like an allergy to the oil, rendering them unsafe for use with that particular person. Of the above EO's, the ones most promising were citronella, catnip, geranium and lemon eucalyptus and various pine needle oils. In folk remedies, tinctures and oils infused with yarrow are common ingredients as well.

The biggest setback with relying on essential oil blends for insect repellency lies in their chemical properties. As volatile chemicals they evaporate very quickly, meaning their scent and repellency is gone in short order. At best, most products appeared to last no more than 30 minutes, requiring repeated application. As the scent disappears, so does the protection. This doesn't mean that using EO's to repel insects is useless; it means we need to use our best judgement when choosing our repellent.

The below recipe for an essential oil based repellent is highly repellent against mosquitoes and ticks, but will be short lived. Expect to reapply within the hour of the first application. It is safe for use on adults and children over the age of 3. If you will be outside for a long duration (i.e., going camping or spending a day hiking in the woods) you may be better off using a DEET product as you'd likely need apply it only twice. It does not include the use of catnip which is presently being touted as THE bug repellent essential oil. It is a rather expensive bottle of oil to buy, often around $60 for 15mL (possibly more depending on the source). It is Whole Family Friendly, however and may be a good investment for the more serious user.
  You could replace Geranium with Lavender or Peppermint.

Bug Repellent with Oil base, 2.5% essential oil blend
120mL             Natural oil (soybean oil is a suggested bug repellent according to Canada Health) such                            as sunflower seed oil, fractionated coconut oil, or jojoba oil.

22d                  Patchouli essential oil

11d                  Geranium essential oil

27d                  Citronella essential oil

References

Trongtokit Y et al.(2005) Comparative repellency of 38 essential oils against mosquito bites. Phytotherapy Research 19(4), 303-9.

Misni N, et al. (2017) Repellent effect of microencapsulated essential oil in lotion formulation against mosquito bites. Journal of Vector Borne Disease 54(1):44-53

https://www.cdc.gov/lyme/prev/natural-repellents.html Accessed June 3, 2018

https://www.canada.ca/en/health-canada/services/about-pesticides/insect-repellents.html Accessed June 7, 2018