Bye, Ticks: An Eco-Friendly Approach to Repellency

Due to climate change, Canada’s blacklegged tick season and population are expanding. The blacklegged tick (Ixodes scapularis) is the only established species in Canada known to transmit Lyme disease, Anaplasmosis, Babesiosis, and Powassan virus. In Canada, Lyme disease cases—caused by Borrelia burgdorferi—are increasing as tick populations grow, raising concern about effective and environmentally safe prevention methods.

Blacklegged ticks are nearly blind and rely on Haller’s organ on their front legs to detect hosts through chemosensation, the ability to sense environmental chemicals and smells. This system can be disrupted by certain scents, meaning plant compounds and essential oils may interfere with host detection and act as natural repellents. While DEET is effective, it does not break down easily in the environment and can negatively affect aquatic ecosystems, making biodegradable alternatives worth exploring. Some people may also have an allergic reaction to DEET.

The purpose of this project is to develop and test eco-friendly, skin-safe tick repellents based on essential oils that may repel blacklegged ticks while being biodegradable. The hypothesis is that certain essential oils, at safe concentrations, can disrupt tick chemosensation and reduce host-seeking behaviour. This research supports safer, more sustainable ways to reduce the risk of contracting tick-borne diseases while minimizing environmental impact.

I began by selecting two strongly scented essential oils, Cinnamon and Rosemary, and conducted preliminary skin sensitivity testing to identify safe concentrations before experimenting with ticks.

In the first round, 3%, 4% and 5% v/v dilutions in Fractionated Coconut Oil were applied to the forearms of three volunteers. Skin reactions (redness and itching) were monitored at 10, 20, and 30 minutes; no irritation was observed, so these concentrations were deemed safe for further testing.

I then evaluated tick repellency by applying each solution to the edges of a square arena. Three blacklegged ticks were introduced, and their movement was recorded at 3, 5, and 10 minutes. Repellency was assessed based on whether ticks crossed the treated barrier and the time taken to do so. Solutions tested included: Rosemary and Cinnamon essential oils (3%, 4%, 5%), alongside Fractionated Coconut Oil (a negative control) and DEET 25% v/v (the positive control).

I decided to expand my project by increasing concentrations of Rosemary and Cinnamon oils and adding four additional essential oils: Helichrysum, Star Anise, and May Cheng (from India and from China). Grapeseed oil replaced coconut oil as a scent-free solvent.

A second round of skin testing on the same three volunteers showed mild irritation from higher cinnamon concentrations, so its maximum was reduced to 15% v/v. The other oils were prepared at 25% v/v. These formulations were retested for tick repellency using the same arena method and observation intervals.

Based on the repellency results, May Cheng (India) at 25% v/v was the most promising repellent. To fully confirm safety, I conducted one final round of skin sensitivity testing with 50 additional participants recording any reactions at 10, 20, and 30 minutes.

The tick repellency experiments revealed clear differences between the essential oils tested, showing that both the type of oil and the concentration strongly influence effectiveness. May Cheng (India) at 25% consistently repelled 66.7% of ticks (2/3 ticks) in every trial, making it the most reliable natural repellent in this study. These results suggest that chemical composition and the oil's scent likely interfered with the ticks’ ability to detect a host.

Other oils were far less effective. They repelled few ticks, and in some trials, no ticks at all. This shows that not all strong-smelling oils automatically repel ticks, and that scent type and chemical compounds of the oils are more important than simply using a higher concentration or strong smell.

DEET at 25% v/v, the chemical positive control, initially repelled 66.7% of ticks at 3 and 5 minutes, but by 10 minutes, suprisingly, failed to repel any ticks. In my testing conditions, May Cheng (India) at 25% v/v ended up performing better than DEET at 25% v/v.

May Cheng (India) at 25% was then tested for skin sensitivity on 53 volunteers and no reactions or discomfort were reported. The test showed that May Cheng (India) shows promise to be safe for people at the concentration tested.

The hypothesis was proven: certain essential oils, when diluted to skin-safe concentrations, can effectively repel ticks.

A few limitations were: each trial only used three ticks, which means the results might not perfectly represent how ticks generally behave, and also the relatively small sample size of only 53 participants for skin sensitivity testing. As the tests were conducted under controlled temperature and humidity conditions, the change of such conditions in the wild could affect tick activity.

Overall, the initial data indicated May Cheng (India) is a good candidate for natural, eco-friendly tick repellent. It didn't show irritation on skin when tested on 53 volunteers and provided measurable, sustained repellency under lab conditions. The other oils tested were much less effective in repelling blacklegged ticks, highlighting the importance of choosing oils based on chemical properties rather than scent strength alone.

This project successfully tested the effectiveness of several natural essential oils as tick repellents, focusing on female Blacklegged ticks (Ixodes scapularis).

The results showed that May Cheng (India) essential oil at 25% v/v was the most effective essential oil out of the ones tested, achieving consistent repellency against Blacklegged ticks.

Skin sensitivity tests showed that this essential oil can be fairly safe for human skin at a certain concentration.

These findings support the idea that carefully selected essential oils could offer a safe, natural alternative to chemical tick repellents.

This research has a real-world application potential. As tick populations and cases of tick borne illnesses continue expanding in Canada, and common chemical repellents can be harmful for the environment, more research into natural prevention strategies is becoming important.

Natural tick repellents could not only effectively protect people from ticks and diseases they carry, but at the same time reduce environmental contamination in comparison to synthetic chemicals and offer safer options for people who are allergic to DEET.

In the future, skin testing on a larger and more diverse group of people could provide even more reliable data on the safety of May Cheng (India)'s essential oil formulation. Additional trials could also explore longer exposure times, seasonal effects on tick activity, doing field testing or experimenting on nymph-stage ticks to better simulate real-world conditions. Doing a detailed test on the specific chemical composition of the particular oil to determine the exact percentage of each component in May Cheng (India) (The exact one I used), could be useful and ensure that this experiment could be easily replicated.

Acknowledgements

Thank you to my family for supporting me throughout my entire project, and driving me around to do my experiments!

I'm very grateful to my mentor and supervisor in the lab in Acadia University, Dr. Nicoletta Faraone, for creating such a supportive environment and letting me use her equipment! I appreciate it so much!

Many thanks to my science teacher Mrs. Sarah Kuehm for all the tips and for being my scientific supervisor!

Thanks to all who participated in the skin sensitivity trial for trusting me and lending me their arms!

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