Natural Insect Repellent: Peppermint's Role

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Introduction

If you have ever been bombarded with persistent and pesky insects that will not go away no matter what you try, this article may be for you. In it, you can read about the role of peppermint in providing a repellent effect. This article will go through the current evidence for peppermints' role as an insect repellent and hopefully be beneficial to you in deciding whether or not to opt to use peppermint. 

Insects and illnesses

Insects are of tremendous benefit to ecosystems and life on the planet as we know it. However, pest insects, particularly, can also cause a substantial amount of damage to humans - both economically and by threatening our physical health. They can be breeding grounds for viruses, bacteria and parasites that use these insects as reservoirs to transmit infection to us. Most insects that carry these potentially deadly infections are bloodsucking insects that pass on their infection while obtaining a blood meal from a host. Any infection carried by that host can then be passed on from the host to the insect who will then further infect others in subsequent meals. There are many insects that feed on blood such as mosquitoes, fleas, lice and ticks. Every year, there are more than 700,000 deaths resulting from diseases transmitted by these insects. Of these, by the largest margin, mosquitoes are the cause of the most illness and death.

Since the dawn of humanity, we have had to live alongside a large array of insects. While most insects are harmless to humans, there has always been the existence of blood-sucking insects. It is only natural for humans to wish to repel these insects that cause annoyance by their persistent presence and potentially detrimental health impacts. This has been done for the longest time by physically swatting them or through the application of natural substances to the skin. However, since the linking of these insects with serious diseases, there have been generations of people experimenting with plant-based repellents in order to keep the problem at bay. Peppermint is one of these plants that have been observed to be effective, especially against mosquitoes but also other insects such as spiders, moths, fleas, cockroaches, ticks and flies.1

Understanding Peppermint

Peppermint is a species of mint that is a cross between watermint and spearmint. It was first identified and classified in England in the late 1600s, but this is not its origin as it has been known to be used in ancient times. The reason it is called ‘pepper’ mint is because of its spicy flavour. It is a plant of European origin and has been held in high regard by many in Europe throughout the ages.  It was usually used for its scent around the house or, particularly in ancient Greece, it was used in baths as it was believed to strengthen the body.

Physically, the peppermint plant has dark green leaves with red veins. The leaves and stems are typically slightly fuzzy. Flowering season lasts from mid-to-late summer with the flowers being purple and produced in whorls.

Peppermint is a versatile plant with many recorded uses. The leaves can be used directly in a preparation called peppermint tea. It is also used in other foodstuffs as flavouring such as in ice cream, sweets, and preserves. Additionally, it is commonly used in hygiene products such as toothpaste, shampoos, soaps and skincare products.

How peppermint repels insects

Peppermint has a high concentration of menthol, menthone, methyl esters and a compound called pulegone, concentrations of which vary depending on the variety of peppermint plant in question. The highest of which is usually menthol with a typical concentration in excess of 80%.

Insects detect smells through their antennae as this is where most of their olfactory receptors are located. Through these antennae they can receive a large variety of molecules and can distinguish between a vast array of different kinds of molecules. In fact, smell plays a large role in communication for most insects. 

The exact mechanism as to how peppermint oil repels insects has not yet been elucidated. In mosquitoes, and by extension other insects, it is thought that the compounds, in particular menthol, disrupts the olfactory receptors in the insects, thereby not allowing them to be able to detect human scent and latch on for feeding.2 Put simply, the peppermint confuses the smell senses of insects and does not allow them to smell their intended host.

Just how effective is peppermint?

In a study carried out to assess the effectiveness of peppermint oil as a mosquito repellent, a fixed volume of water in a 6 x 4 inch tray filled to a depth of 3 inches was tested with peppermint oil to see what effect it has on the mosquito larvae. The published result demonstrated that for three common disease-transmitting mosquito species, 4 ml of peppermint oil per metre squared of water surface was enough to cause 100 percent mortality to all the mosquito larvae involved.3 Application of 0.1 ml of the oil to an arm produced 100 percent protection for 150 minutes (2 hours and 30 minutes) in another study.4 Thirty minutes after that, it produced a reduced rate of bites on the arm with oil as compared with the control arm. 

Using peppermint repellent

When it comes to peppermint as a repellent, there are a number of ways that it can be used: 

  • The leaves can be placed near an area you wish to repel insects. 
  • If you are aware of insect movements inside your house and the route they usually take, either through a crevice under a skirting board or windowsill, the distinctive peppermint smell may be all that is needed to ward away unwanted visitors to your home without resorting to killing these bugs. This is an excellent option for those who are vegan and do not wish to kill these insects but only to deter them. 
  • For application to the body, peppermint can be purchased either as a spray to spray onto the skin or as an oil which is rubbed in after applied to the skin surface. 

Given that peppermint’s repellent effects stop working after a certain period, it is best to reapply consistently for a continued repellent effect. Each product will have instructions to guide how often this may be. It is important, therefore, to read the specific set of directions on the product box or inside its leaflet. Carry out a patch test to check for allergy before use in the interest of safety.

Peppermint vs synthetic chemical repellents

The downside of using peppermint, as compared to synthetic chemical repellents, is that it evaporates much more quickly from the skin. Meaning it may not be effective for long unless there is continued application. Also, peppermint cannot overload all of the smell receptors that insects have, which means it may be ineffective to certain insects depending on their receptor type. Thus, the effectiveness will depend on the formulation and concentration of the product.

DEET (chemical name, N,N-diethyl-meta-toluamide), which is a widely used ingredient in synthetic insect repellent, typically provides much longer lasting protection. With regards to the environment, peppermint oil is considered to be less harmful as it is readily biodegradable and does not persist for as long in the environment. It is also less toxic to fish in a comparable quantity as compared to DEET. 

Peppermint and allergies

Allergies to mint plants and peppermint aren’t common. However, there is always a potential for any new ingredient that you have not tried before to cause an allergic reaction. An allergic reaction can range from mild to severe and life-threatening. It is important to know the signs and seek help if necessary.

Safe usage

Avoid contact of peppermint oil with eyes and mucous membranes. It is a good idea to always perform a patch test on children or pets to see if there is any adverse reaction. It is best to apply the oil to an item of clothing or bedding for children or collars for pets. This can reduce the potential for any unwanted reaction or sensitivity with the skin. 

Most importantly, pay attention to your children or pets after application and look for any signs of discomfort or distress. If an issue arises then discontinue use immediately.

If you are pregnant or breastfeeding, it is always best to consult your healthcare professional who can guide you as to whether it is safe to use during pregnancy and breastfeeding.

Summary

There are many natural alternatives for repelling insects. Peppermint, particularly peppermint oil, has a proven track record of being able to provide the repellent effect needed for many different types of insects including mosquitoes. One caveat to bear in mind is that the duration of the effect will be limited by the concentration of the peppermint oil and how often it is applied. It is best to follow instructions provided on the product for the best result. Also, it is worth bearing in mind that there will be no guarantee that peppermint will provide a one hundred percent repellent effect and there will be a discrepancy based on geographical location and the species of insect.

References

  1. Asadollahi A, Khoobdel M, Zahraei-Ramazani A, Azarmi S, Mosawi SH. Effectiveness of plant-based repellents against different Anopheles species: a systematic review. Malar J [Internet]. 2019 [cited 2024 May 5]; 18(1):436. Available from: https://malariajournal.biomedcentral.com/articles/10.1186/s12936-019-3064-8.
  2. Barnard DR. Repellency of Essential Oils to Mosquitoes (Diptera: Culicidae). J Med Entomol [Internet]. 1999 [cited 2024 May 6]; 36(5):625–9. Available from: https://academic.oup.com/jme/article-lookup/doi/10.1093/jmedent/36.5.625.
  3. Ansari MA, Vasudevan P, Tandon M, Razdan RK. Larvicidal and mosquito repellent action of peppermint (Mentha piperita) oil. Bioresource Technology [Internet]. 2000 [cited 2024 May 6]; 71(3):267–71. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0960852499000796.
  4. Kumar S, Wahab N, Warikoo R. Bioefficacy of Mentha piperita essential oil against dengue fever mosquito Aedes aegypti L. Asian Pacific Journal of Tropical Biomedicine [Internet]. 2011 [cited 2024 May 6]; 1(2):85–8. Available from: http://linkinghub.elsevier.com/retrieve/pii/S2221169111600014.

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Peter McGowan

Medicine( M.B, B,Ch), University of Galway, Ireland

I am a medical graduate interested in writing and discovery at the boundaries of current knowledge. I have a particular interest in personalised medicine. I believe that it is important to convey information accurately and effectively to allow it to be understood and help draw insights that can expand upon our ever-growing collective body of knowledge.

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