Insect Deterring Essential Oils

In September 2014, Health Canada , rather abruptly,

‘…ordered citronella-based bug sprays pulled from shelves across Canada, citing a lack of research into the safety of their products.’

Just as abruptly, in December 2014, Health Canada reversed this decision.

Manufacturers and scientists were perplexed by the decision, and I understand why.

“The sudden shift has exasperated not only manufacturers, but also scientists. They wonder why Health Canada shunned their original recommendation that citronella oil was generally safe.’

When I first learned about ‘the ban’, it felt to me, a push-back from the big companies who manufacture deet-based bug sprays.  Citronella-based and other essential oil-based products would have most certainly been affecting their bottom-line.   It would appear, quite deeply affecting their bottom-line.   This is my opinion, as someone who has spent considerable time researching the bug deterring properties of essential oils.

Oh how the tides have changed since 2014.  For those wanting a non-toxic alternative to conventional insect repellents, check-out Health Canada’s list on a page entitled ‘Insect Repellents’ (last updated in the summer of 2016). We now find essential oils listed as both insect repelling and safe:

Insect repellents with a mixture of lemon, eucalyptus, pine needle, geranium and camphor essential oils:

  • can be used safely when applied as directed to repel mosquitoes
  • should not be used on children younger than 2 years old

The key here, as a certified aromatherapist, is the term ‘mixture’. In aroma-language, we translate this to mean a ‘blend’. Health Canada has deemed the synergistic effect of lemon, eucalyptus, pine needle, geranium and camphor essential oils as a blend to be an effective insect repellent.  Amazing.  Only in terms of Health Canada drawing this conclusion. Qualified aromatherapists and lay-folk both, already knew this.

Of note, citronella is now listed to be an effective repellent of mosquitoes and eucalyptus citriodora, aka lemon eucalyptus, was found to be an effective repellent of mosquitoes and black flies.

What’s missing: Safety information about lemon essential oil; it is known as being ‘phototoxic’ which means when applied directly to the skin and then the skin is exposed to sunlight, you risk burning your skin.   Personally, I would not be adding this to my DIY insect deterring blend. Had their been a qualified aromatherapist on the expert panel assembled by Health Canada, this would have been highlighted as a safety concern with the use of lemon essential oil on the skin.  Sprayed on clothing is safe.

What’s also missing: Concentration level.  In aroma-language, how many drops of each essential oil ought to be added to what type of carrier base in order to be effective.

If you are looking for a pre-blended insect deterring blend, please check out my LJ Turtle Let Me Be Outdoor Meditation Spray.

And if you are curious about the evidence-based literature on the subject, here is what I dug-up on the scientific research conducted on the efficacy of a wide range of essential oils with insect deterring properties.

Happy blending and best of luck deterring the outdoor pests that our Canadian summers bring.

 

Bioactivity-Guided Investigation of Geranium Essential Oils as Natural Tick Repellents

J. Agric. Food Chem., 2013, 61 (17), pp 4101–4107

Abstract

The evaluation of 10 essential oils of geranium, Pelargonium graveolens (Geraniaceae), were all shown to have repellent activity against nymphs of the medically important lone star tick, Amblyomma americanum (L.). The biological tests were carried out using a vertical filter paper bioassay, where ticks must cross an area of the paper treated with repellent to approach host stimuli. One of the essential oil samples that repelled >90% of the ticks at 0.103 mg/cm2 was selected for further fractionation studies. The sesquiterpene alcohol, (−)-10-epi-γ-eudesmol, was isolated and identified by spectral methods. (−)-10-epi-γ-Eudesmol at 0.103 and 0.052 mg of compound/cm2 of filter paper repelled 90 and 73.3% of the ticks, respectively. (−)-10-epi-γ-Eudesmol exhibited similar repellency to the reference standard N,N-diethyl-meta-toluamide (DEET) at concentrations of ≥0.052 mg of compound/cm2 of filter paper, with (−)-10-epi-γ-eudesmol losing much of its repellency at 0.026 mg of compound/cm2 and DEET at 0.013 mg of compound/cm2. Isomenthone and linalool did not repel ticks at the concentrations tested. Most repellents are marketed with much higher concentrations of active ingredient than the concentrations of the natural repellents tested herein; therefore, effective compounds, such as (−)-10-epi-γ-eudesmol, found in geranium oil, have the potential for commercial development.

Development of Melaleuca oils as effective natural‐based personal insect repellents

Australian Journal of Entomology. 2010. Volume 49, Issue 1.

Abstract

For many decades effective insect repellents have relied on synthetic actives such as N,N‐diethyl‐meta‐toluamide. Increasingly, consumers are seeking natural‐based alternatives to many everyday products including insect repellents. While many studies have been published detailing the potential of essential oils to act as insect repellents, few oils have been identified as viable alternatives to synthetic actives. This study details the process involved in the selection of Australian essential oils effective as repellents and the subsequent testing of natural‐based insect repellents using the selected oils. Using a combination of laboratory‐based and field‐based testing, oil from Melaleuca ericifolia was identified as being an effective insect repellent. When formulated into three different bases: an alcohol‐based spray, an emulsion and a gel, these Melaleuca‐based repellents were shown to be as effective at repelling mosquitoes Aedes vigilax (Skuse) (Diptera: Culicidae) and Verrallina carmenti (Edwards) (Diptera: Culicidae), the bush fly Musca vetustissima (Walker) (Diptera: Muscidae), and biting midges Culicoides ornatus (Taylor) (Diptera: Ceratopogonidae) and Culicoides immaculatus (Lee & Reye) (Diptera: Ceratopogonidae) as a synthetic‐based commercial repellent. This study has shown that effective insect repellents based on natural active ingredients can deliver repellency on par with synthetic actives in the field. Three Melaleuca‐based formulations have been registered as repellents and are now commercially available.

PLANT ESSENTIAL OILS AS MOSQUITO REPELLENT – A REVIEW

IJRDPL – Vol 3, issue 1 (2013), December – January. Pages: 143-150

Abstract

Malaria is considered endemic in 104 countries and territories around the world nessessitating its control. Essential oils belonging to various plant species and possessing mixtures of hydrocarbons have been seen to act as effective repellent against various pests. The monoterpenoids constituting the major component is found to be cytotoxic to plant and animal tissue thus impairing the normal functioning of these tissues. The commercially marketed repellents basically consist of essential oils from plants Cymbopogon nardus, Eucalyptus maculata, Cymbopogon excavatus, Mentha piperita, Azadirachta indica. The volatile nature of these components due to their short duration of efficacy has urged for the development of novel formulations, use of fixatives such as vanillin and combination essential oil plants as repellents. The easy availability and less adverse environmental impact have led to the increased interest in plant origin insecticides as an alternative to chemical insecticides. The present article envisaged to review the reports of essential oils on its effectiveness as repellent.

Mosquito Repellent Actions of the Essential Oils of Cymbopogon citratus, Cymbopogon nardus and Eucalyptus citriodora: Evaluation and Formulation Studies

Journal of Essential Oil Bearing Plants. Volume 15, 2012 – Issue 5

Abstract

Essential oils extracted by steam distillation from Cymbopogon citratus (DC.) Stapf, Cymbopogon nardus (L.) Rendle and Eucalyptus citriodora Hook were evaluated for their repellent effects against Anopheles arabiensis mosquitoes under laboratory conditions. Blended oils, ointments and cream formulations of the oil of C. nardus in different bases were also evaluated. At 10 % and 20 % concentrations, all the oils showed a minimum of 90 % and 95 % relative protection, respectively, soon after application. These were not significantly different in efficacy from NN-diethyl-meta-toluamide (DEET), P<0.05. Afterwards however, only C. nardus oil produced more than 70 % protection for 3 h and 4 h at a concentration of 10 % and 20 %, respectively. Combinations of 10 % or 20 % of each of the oils of C. citratus and C. nardus gave better protection than their individual effects. In the presence of the oil of E. citriodora, the effects of C. citratusand C. nardus were significantly reduced at both concentrations. The oil of C. nardus in oleaginous ointment (i.e. Vaseline) provided above 80 % relative protection for as long as 4 h which was better than the effect of the 20 % oil, P<0.05. Similarly, the oil in hydrophilic ointment, 1:1 w/w blend of PEG 4000 and PEG 600, gave better repellent effect than the 20 % oil (P<0.05). However, the effect of the o/w cream was not statistically different from the 20 % oil, P>0.05. The blends of C. citratus and C. nardus oils and the ointment formulations of the oil of C. nardus showed improvement on the percentage of protection of the oil of C. nardus. However, both the blending and the formulations did not improve the duration of protection. In addition, both the percentage and duration of protection were not as good as DEET, P<0.05. This study demonstrated the potential of essential oil of C. nardus as topical repellent against An. arabiensis.

Investigation of the Repellence Activity of Bio-Out, a Natural Mosquito Repellent

Int. J. LifeSc. Bt & Pharm. Res. 2013. Vol. 2. No. 3.

Abstract

Mosquito repellents are important tools for prevention of dreadful diseases as well as painful mosquito bites. Lemongrass essential oil (Cymbopogon citratus) has been investigated for its repellent activity against mosquitoes respectively. Tests were performed with out the contribution of human volunteers. Number of visible mosquitoes was noticed. Approximately 80% repellence activity has been observed. Lemongrass oil exhibited an average of 30 min protection time against mosquitoes to make them away from the observed area, All-out (50-80%) protection time in comparison to the activity of the best known chemical insect repellent, N, N-diethyl-mtoluamide (DEET). Determining the effectiveness of lemon grass (Cymbopogon citratus) as mosquito repellent is the main goal of the study. Specifically, it intends to apply the extraction procedure techniques to extract the essential oils of lemon grass. It can be concluded that lemon grass oil is a promising natural repellent due to its safety advantage over chemical repellents.

The effects of plant essential oils on escape response and mortality rate of Aedes aegyptiand Anopheles minimus

Journal of Vector Ecology. 2015. Volume 40, Issue 2

Abstract

Insecticide resistance and growing public concern over the safety and environmental impacts of some conventional insecticides have resulted in the need to discover alternative control tools. Naturally occurring botanically‐based compounds are of increased interest to aid in the management of mosquitoes. Susceptible strains of Aedes aegypti (Linnaeus) (Diptera: Culicidae) and Anopheles gambiae(Meigen) (Diptera: Culicidae) were treated with permethrin, a common type‐I synthetic pyrethroid, using a discriminate dose that resulted in less than 50% mortality. Piperonyl butoxide (PBO) and 35 essential oils were co‐delivered with permethrin at two doses (2 and 10 µg) to determine if they could enhance the 1‐h knockdown and the 24‐h mortality of permethrin. Several of the tested essential oils enhanced the efficacy of permethrin equally and more effectively than piperonyl butoxide PBO, which is the commercial standard to synergize chemical insecticide like pyrethroids. PBO had a strikingly negative effect on the 1‐h knockdown of permethrin against Ae. aegypti, which was not observed in An. gambiae.Botanical essential oils have the capability of increasing the efficacy of permethrin allowing for a natural alternative to classic chemical synergists, like PBO.

Essential Oil Repellents- A short Review

Int. J. Drug Dev. & Res. April – June 2014. Vol. 6. Issue 2.

Abstract

Mosquitoes are the most important of insects in terms of public health importance which transmit a number of diseases such as dengue, chikungunya, Japanese B encephalitis, filariasis and malaria, causing millions of deaths every year. Mosquito control and personal protection from mosquito bites are currently the most important measures to prevent these diseases. Essential oils from plants have been recognized as important natural resources of insecticides because some are selective, biodegrade to non-toxic products and have few effects on non-target organisms and environment. Essential oils are volatile mixtures of hydrocarbons with a diversity of functional groups, and their repellent activity has been linked to the presence of mono – terpenes and sesquiterpenes. In some cases, these chemicals can work synergistically, improving their effectiveness. The aim of this review is to highlight the significance of essential oil from Cymbopogon winterianus Jowitt, Azadirchata indica, Lavandula angustifolia, Mentha piperita for control of vector- borne disease.

 

Plant-based insect repellents: a review of their efficacy, development and testing

Malar J. 2011; 10(Suppl 1): S11.

Abstract

Plant-based repellents have been used for generations in traditional practice as a personal protection measure against host-seeking mosquitoes. Knowledge on traditional repellent plants obtained through ethnobotanical studies is a valuable resource for the development of new natural products. Recently, commercial repellent products containing plant-based ingredients have gained increasing popularity among consumers, as these are commonly perceived as “safe” in comparison to long-established synthetic repellents although this is sometimes a misconception. To date insufficient studies have followed standard WHO Pesticide Evaluation Scheme guidelines for repellent testing. There is a need for further standardized studies in order to better evaluate repellent compounds and develop new products that offer high repellency as well as good consumer safety. This paper presents a summary of recent information on testing, efficacy and safety of plant-based repellents as well as promising new developments in the field.

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