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DEET

technology Maturity 11-13 Next article →

DEET is one of the most effective and widely used active ingredients in commercial insect repellents. Its full chemical name is N,N-Diethyl-meta-toluamide, though it is often called diethyltoluamide. It is a liquid that appears colorless or slightly yellow. People apply this oil to their skin or their clothing to prevent bites. It provides protection against many invertebrates. These include mosquitoes, biting flies, ticks, fleas, chiggers, and leeches. It can even protect against some parasitic worms. Because it helps prevent the spread of pathogens, it is a vital tool for public health.

Preparation of DEET
Preparation of DEET

Scientists are still researching the exact mechanism of how DEET works. There are several leading hypotheses regarding its function. The "smell and avoid" hypothesis suggests that DEET has an unpleasant odor to insects. The "bewilderment" hypothesis proposes that the scent confuses the insect's sensory systems. Another idea is that DEET acts as a mask. It may reduce the volatility of skin odorants that usually attract insects to humans. Additionally, mosquitoes may be repelled through physical contact with chemosensory hairs on their legs. In some cases, DEET can also have neurological effects on insects.

Concentrations of DEET in consumer products vary widely. They can range from less than 10% to nearly 100%. Higher concentrations generally correlate with more hours of protection. However, using a concentration greater than 50% does not increase the duration of protection. The Centers for Disease Control and Prevention (CDC) recommends using 30% to 50% DEET to prevent insect-borne diseases. In the United Kingdom, the National Health Service (NHS) suggests a 50% concentration for travelers visiting areas with malaria. For infants and children, a lower 10% concentration is often recommended.

Safety guidelines are important when using DEET. The CDC advises that DEET should not be used on children younger than 2 months old. Health Canada has specific rules for children as well. They recommend that children between ages 2 and 12 use concentrations of 10% or less. They also suggest that children under 2 should receive no more than one application per day. While DEET has a remarkable safety profile with nearly 8 billion human applications, it can cause irritation. It may irritate the eyes or cause breathing difficulties and headaches. In very rare cases, it can cause severe epidermal reactions. It should never be applied under clothing or on damaged skin.

Preparation of DEET
Preparation of DEET

DEET has a significant history rooted in military necessity. It was developed in 1944 by Samuel Gertler at the United States Department of Agriculture. The United States Army needed a solution for jungle warfare during World War II. It entered military use in 1946 and became available for civilian use in 1957. Soldiers in Vietnam and Southeast Asia used early versions. One early mixture was called "bug juice," which contained 75% DEET and 25% ethanol. Later, a more advanced formulation was created using polymers to reduce evaporation. This extended-release version was registered by the Environmental Protection Agency (EPA) in 1991.

Users should be aware of how DEET interacts with other materials and substances. DEET is an effective solvent. This means it can dissolve certain materials like watch crystals, plastics, and nail polish. It can also damage synthetic fabrics such as rayon, spandex, acetate, or dynel. It may act as a plasticizer, leaving some hard plastics feeling soft and flexible. When using sunscreen, you should wait at least 30 minutes after application before applying DEET. This is because combining the two can decrease the sunscreen's protection factor by about one third. It also increases the absorption of both substances into the skin.

Preparation of DEET
Preparation of DEET

Finally, DEET has specific impacts on the environment. While it is not expected to bioaccumulate, it shows slight toxicity to certain freshwater life. It can be toxic to species like rainbow trout, tilapia, and some freshwater zooplankton. In 1991, studies detected DEET in the Mississippi River at levels between 5 and 201 ng/L. Algae colonies are particularly at risk, as they can experience significant biomass decline at 500 ng/L. Fortunately, DEET can be biodegraded by fungi. It breaks down well under aerobic conditions, though it breaks down slowly under anaerobic conditions.

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