An overview of insects repellents

An overview of insects repellents
March 11, 2014 11:44 PM

This article is supposed to be a large overview of insect repellents. You will learn about their active substances, the way they work and other useful information about them.

An introduction to insect repellants

Certain chemicals that are used to keep insects away and prevent diseases spread by insects are known as insect repellants. There is a large variety of insect repellents available. These chemical substances have quality of repelling many groups of insects like mosquitoes, ticks, mites etc. Some chemicals are used exclusively for certain insects. These are used as an alternative to insecticides.

Due to increased resistance against insecticide products and increasing health concerns, insect repellents are now more popular. These are used in various forms like lotions, coils, pads and bands. The main use of insect repellants is for body protection against infectious diseases like malaria. In the following text, we will be reviewing the different aspects related to the insect repellents.

What Do Insect Repellents Do?

Not only do insect repellents keep mosquitoes, ticks, gnats and alternative bugs away but also act as a safe and effective way to stop insect-borne diseases. Mosquitoes, alone, are the biggest cause of deaths worldwide. According to some estimates, over 1,000,000 individuals worldwide die from mosquito-borne diseases once a year. Insect repellents are very useful to stop bites, skin eruptions and rashes which will be caused by an insect's bite. Mosquito bites can cause severe skin irritation through an allergic reaction to the mosquito's saliva.

Authorities, like the center for malady control and interference (CDC) recommend the utilization of insect repellents to stop mosquito-borne diseases. In the twentieth century, malaria was eradicated within the temperate area of the world with the utilization of insecticide and alternative insect powder pesticides.

However, roughly 400th of the world's population in tropical regions is also exposed to malaria. Over 1,000,000 deaths and up to five hundred million cases of malaria are still reported annually within the world, with one kid dying each forty seconds due to malaria. Stats are alarming, right?

Use of sprays is an option but these insecticides are harmful to human beings too. In most cases, these chemicals do more harm than good. Repellants, on the other hand, have minimal side effects.

Main ingredients of insect repellents

Different chemicals have been employed in the past as insect repellents and there is a continuous research going on to find a good product with minimum negative effects and better efficiency. Below are some main ingredients that are used either alone or in combination with other chemicals to make an effective insect repellent product:

  • DEET
  • Picardin
  • Permethrin
  • IR3535
  • Oil of lemon eucalyptus

Being members of different chemical groups, these agents have different effects and properties. The side effects also vary from one to other.

DEET

DEET is an abbreviation for N, N-Diethyl-meta-toluamide. DEET is the most commonly used insect repellent and it is an active ingredient of mot of insect repellent products. It is mainly applied to skin or clothes for protection against disease carrying insects. It has the ability to repel a number of insects like mosquitoes, ticks, fleas and chiggers. It was made by the US army as a war weapon, but it became popular as an insect repellent following its jungle warfare results.

DEET works by ‘blinding’ the insects’ senses for certain chemicals that are mainly present in human secretions. It blocks the olfactory receptors of insects for the 1-octen-3-ol, a substance found in human sweat and breath. The advantages and side effects caused by DEET vary with its used concentrations. It has different effect at different concentrations. The main advantage provided by DEET is its promising efficiency and the ease to its use.

However, following are the sides effects linked to this repellant: o Skin irritation and rashes due to its ability to penetrate the skin o Melting of some synthetic products like glasses, shoes etc. o DEET smells bad o Health problems such as rare encephalopathy in children You should avoid excessive and prolonged application of DEET in strong concentration. Using a low concentration of this repellent is safe and effective too. DEET should especially be applied to well-ventilated parts of body.

Picardin

Picardin is also known as icardin and it is an odorless and colorless insect repellant. Its chemical name is 1-piperanidinecarboxylic acid. It is also named as Bayrepel as it was developed by the German company Bayer. Picardin is reported to be as effective as DEET and it is devoid of the skin irritation effects, as caused by DEET. According to the world health organization, picardin is superior to DEET in terms of safety and efficacy. The mechanism of picardin is also similar to the DEET as it works by blocking sensory system of insects. It does not kill insects but repels them making them less likely to bite.

Some of the major benefits of picardin are:

  • It is more comforting as it does not have any odor or color
  • It has fewer side effects as compared to DEET
  • More friendly for children due to safety

Skin irritation is the main complication associated with picardin. The irritation gets worse when picardin comes into contact with eyes. Main problem with picardin is its short half life i.e. its effect doesn’t last long. It does not last as long as standard repellants. Its half life is about 40% of that of DEET.

Permethrin

Permethrin is one of the most common chemicals used as insect repellents. It is also an insecticide for some insects. It belongs to the pyrethroids group of synthetic chemicals and acts as a neurotoxin for insects. It is also used as a remedy for scabies where its 5% cream is applied on the affected skin. It has additional benefits of being poorly absorbed by skin and low toxicity in humans.

Permethrin has a different mechanism of action as compared to DEET and picardin. It acts as a neurotoxin and slows down the nervous activities of targeted insect by binding to the current conducting channels. Permethrin should be used with more caution due to its toxicity for animals in addition to insects. It shows more pronounced and damaging effects on cold-blooded animals as compared to warm-blooded such as mammals including humans. It is extremely damaging for aquatic life and can kill the fish so care should be taken in this regard. It has the potential to kill the animals like cats too. If very high doses of permethrin are used, humans are also at risk for developing toxicity of permethrin. It is a stable agent with a long half life of about 70 days. Human exposure to large doses of permethrin causes certain symptoms and can also be fatal in severe cases.

Following signs and symptoms are the indicatives of permethrin toxicity:

  • Nausea, headache
  • Muscle weakness
  • Excessive salivation
  • Shortness of breath
  • Seizures

In cases of suspected exposure, permethrin levels can be estimated in blood and urine to confirm the toxic effects of this insect repellent.

IR3535

IR3535 is a synthetic insect repellant and is a newer insect repellent. Its chemical name is 3-[N-Butyl-N-acetyle]-aminopropionic acid. It was developed in the mid-70s by Merck and company. However, it was in use in the Europe for about 20 years since it was registered and launched in the US. IR3535 is a good alternative to DEET and it is proved to act well against ticks and mosquitoes. Similar to other insect repellants, it possesses the same skin irritation problem and irritation can be severe if eyes are involved. Structurally based on alanine and beta-alanine, IR3535 is believed not to possess serious toxic effects.

Oil of lemon eucalyptus

The oil from lemon eucalyptus tree has proved to contain insect repellant properties due to its active chemical named as p-methane 3, 8-diol (PMD). Oil is applied on the skin in order to gain protection from mosquitoes and tick bites. In addition to its insect repellent ability, oil from lemon eucalyptus is also used as medicine in the treatment of various conditions like muscle spasms, onchomycosis, osteoarthritis and joint pain. It is said to have same insect repellent quality as DEET but it lags behind in short life. It has a short half life as compared to DEET.

People usually need to apply 30% lemon eucalyptus extract on their skin for about 3 times a day to prevent the insects biting them. Lemon eucalyptus oil is safe to apply on skin and causes no harm to it. However, it should be kept in mind that safety is linked with topical use only. Oral intake of lemon eucalyptus extract can cause seizures and death too.

Safety record of insect repellents

Active ingredient names like DEET, picaridin, and permethrin are effective in clinical trials and are registered for topical application within the U.S. Environmental Protection Agency (EPA) also approves their use as insect repellents when applied on the skin or article of clothing.

Once EPA registers a repellent, they evaluate the product for effectiveness and potential side effects on humans and also the surroundings. An EPA registered insect repellant is not expected to cause serious adverse effects to humans or the setting once used as directed. CDC (centre for disease control) states that DEET and Picaridin insect repellents have advanced degree of effectiveness in scientific, peer-reviewed, literature and products containing these active ingredients generally offer longer-lasting protection than others.

DEET (N, N-diethyl-m-toluamide): Insect repellents containing DEET have been used for more than 40 years to repel mosquitoes, ticks, fleas, biting flies and chiggers. It’s often taken as the "gold standard" of bug repellents.

Picaridin (KBR 3023): Picaridin is roughly as effective as DEET at applicable concentrations, however could also be less irritating.

Oil of Lemon Eucalyptus (p-menthane 3, 8-diol (PMD): Oil of Lemon Eucalyptus, a plant-based repellent, is also registered as a repellent by the EPA. Some researches conducted in the US tested the efficacy of this oil as insect repellent. Results showed that it provided protection just like repellents with low concentrations of DEET.

Permethrin: Permethrin is another repellent that is intended for application on clothing and equipment.

Natural insect repellents

Not all the people use synthetic chemical products to avoid insect bites. There are many natural options that are employed by the people to save themselves from insect related hazards. Many companies are also producing herbal products that contain natural extracts or essential oils. Most of the insect repellents are volatile oils extracted from different plants.

Some of commonly used insect repellents are:

  • Geranium Oil
  • Citronella Oil
  • Rosemary Oil
  • Lemongrass Oil
  • Cedar Oil
  • Peppermint Oil
  • Lemon Eucalyptus Oil
  • Cinnamon Oil
  • Castor Oil
  • Possibly Oils from Verbena, Pennyroyal, Lavender, Pine, Cajuput, Basil, Thyme, Allspice, Soybean, and Garlic
  • Clove Oil

The advantage of natural repellents is that the negative effects can be avoided and these products do no harm to the skin and associated articles like clothes, glasses etc. The disadvantage is that these products need to be applied about three times a day due to short half life and volatile nature.

Conclusion

From above discussion, it can be inferred that there are large number of products that can be applied on skin to prevent the insect bites and related hazards. Every product or chemical has its own specific advantages and disadvantages. Having the best knowledge about such insect repellent products is the basic key to understand the working and different aspects of insect repellants. The need for using such products varies according to geographic areas. It is crucial to use mosquito repellents in an area of excessive mosquitoes to avoid malaria, and insect repellents are the tools to achieve it.

Selection of these products is a subjective matter and people should choose according to the needs and ease of use. The important thing is to acknowledge the possible side effects on body that may become serious in cases of over dosing. Children are more prone to abuse such products and it can produce serious complications. Hence, basic information about major incest repellent chemicals can fulfill the need of choosing and using the best repellant for you.

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Written by: Michal Vilímovský (EN)
Education: Medical student, 3rd Faculty of Medicine, Charles University, Prague, Czech Republic
Published: March 11, 2014 11:44 PM
Next scheduled update: March 11, 2016 11:44 PM
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