Insects play a vital role in ecosystems, but their presence can sometimes turn our outdoor adventures into a nightmare. Mosquitoes, ticks, flies, and other pesky bugs can not only ruin a perfectly good picnic but also pose health risks. In such moments, you might have had an insect repellent shoved to your face and you notice the word “DEET” on it. Then you might wonder what exactly DEET is, and how it shields you from those relentless insect bites.

In this post, we'll delve into what DEET is, shedding light on its history, chemical properties, mechanisms of action, effectiveness, safety considerations, and alternatives.

A peek into its history

First things first, DEET stands for N,N-Diethyl-meta-toluamide. It's a mouthful, we know! But you can simply call it DEET. It was developed by the United States Army in the 1940s as a chemical compound to protect soldiers from insect-borne diseases during World War II. Since then, it has become the gold standard in insect repellents, widely used in both military and civilian applications.

Chemical properties of DEET

Now, let's get a bit technical (but not too much, we promise). DEET is a synthetic compound with a chemical formula of C12H17NO known for its long-lasting effectiveness in repelling a variety of insects, including mosquitoes, ticks, and flies. It's typically a colourless or slightly yellow liquid with a faint odour.

DEET is relatively soluble in organic solvents like acetone, ethanol, and ethyl acetate, however, it is only sparingly soluble in water, which is why it is commonly formulated with other ingredients when used in insect repellent products.

How does DEET work in repelling insects?

It all lies in the chemical structure. Generally speaking, DEET works by masking the scents and odours that attract insects to humans. When applied to the skin or clothing, it creates a vapour barrier that confuses and repels insects. This disruption in their ability to locate and land on a potential host makes DEET an incredibly effective repellent. 

DEET's chemical structure is somewhat more complex. It consists of three main parts:

• Diethyl group: The "Diethyl" part of DEET refers to the presence of two ethyl groups, each containing two carbon atoms and five hydrogen atoms. These diethyl groups are essential for the compound's effectiveness in repelling insects.
• Meta-Toluene group: The "meta-toluene" part of DEET signifies a toluene ring with a methyl group (CH3) attached at the meta position. Toluene is a benzene derivative and is responsible for the faint, characteristic odour of DEET.
• Amide functional group: The "amide" group in DEET contains a nitrogen atom bonded to a carbonyl group (C=O) and a hydrogen atom. This functional group plays a crucial role in DEET's mechanism of action, as it interacts with the insects' olfactory system.

Effectiveness of DEET

Based on research, DEET provides more than 96% protection. According to the Western Australia (WA) Department of Health, the protection time varies according to the concentration of DEET. 

Repellents containing up to 20% DEET:

For everyday outings or those moments when you're enjoying the outdoors during peak mosquito activity around dawn or dusk, products containing less than 10% DEET are your go-to option. They provide around 2 hours of protection, giving you a solid buffer against those persistent biters. If you opt for a product with 20% DEET, you can extend that protection to approximately 4-6 hours.

Repellents containing >20 - 80% DEET:

If your outdoor activity involves extended exposure to insects, like those long fishing or camping trips, products containing 40-80% DEET provide a whopping 8-12 hours of protection. But there's a catch: you should limit the use of high-DEET products to times when you'll be out for an extended period. Applying them too frequently can potentially lead to skin irritation.

Is DEET bad for you?

Now you have also heard or read somewhere that DEET has its own set of side effects that are harmful to human health. DEET is generally considered safe when you use it as directed but there are some potential side effects and adverse reactions to be aware of.

1. Skin irritation - Some individuals may experience redness, itching, or a rash at the site of application. This irritation is typically mild and temporary. 
2. Allergic reactions - In rare cases, individuals may be allergic to DEET, leading to more severe skin reactions. Signs of an allergic reaction may include hives, swelling, and difficulty breathing. 
3. Eye and mucous membrane irritation - DEET should not come into contact with the eyes, mouth, or other mucous membranes. If DEET accidentally gets in the eyes, it can cause irritation, redness, and discomfort.
4. Nervous system effects - High concentrations of DEET applied inappropriately or ingested may lead to nervous system effects, such as dizziness, headaches, and nausea.
5. Severe toxicity - When accidentally ingested in high doses it can cause severe toxicity, leading to nausea, vomiting, bradycardia, seizures, and cardiotoxicity. 
6. Stinging or burning sensation - Some people may experience a mild stinging or burning sensation upon applying DEET, particularly on sensitive or freshly shaved skin. This discomfort usually subsides within a few minutes.
7. Chemical sensitisation - Prolonged or frequent use of DEET, especially in high concentrations, can lead to chemical sensitisation in some individuals. This condition may cause skin reactions to DEET or other chemicals in the future

Does DEET cause cancer?

The question of whether DEET (N,N-Diethyl-meta-toluamide) causes cancer has been a subject of research and debate. There is so far, no conclusive evidence to suggest that DEET is a human carcinogen, meaning that there is no definitive proof that DEET causes cancer in humans.

Is DEET safe for younger children and pregnant women?

For children:

For children older than two months, it is generally considered safe to use DEET-based repellents, but it's important to choose an appropriate DEET concentration, and to not apply it more than once a day. Seizures may happen in small children who have been exposed to DEET over extended periods, particularly in high concentrations. Lower concentrations, typically less than 10%, are recommended for younger children. 

For pregnant women:

DEET is generally considered safe for pregnant women when used as directed. There is no substantial evidence to suggest that DEET poses a significant risk to pregnant women or their developing babies when applied to the skin as an insect repellent.

If you have any concerns about using DEET-based insect repellent on young children or if you’re pregnant, you can explore alternative insect repellents with different active ingredients that are natural and plant-based.

Alternatives to DEET

If you're concerned about the potential health effects of DEET or prefer natural alternatives for insect repellent, there are several options worth considering, and one of them would be using natural insect repellents. They are derived from plant-based ingredients that have the same effect in repelling insects and are often favoured for their gentler formulations. 

They usually come in essential oil forms in itself or added into the formulation for lotions, sprays and the likes, with some of the common ones include:

• Citronella
• Lavender
• Peppermint

These natural alternatives can be a great choice for those seeking DEET-free options, however, it's essential to understand their effectiveness may vary, and they may need more frequent reapplication than synthetic repellents. Ultimately, it’s all on you to consider your specific needs and circumstances when choosing the right repellent for you.

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Insect Repellent Travel