Throughout the world, arthropods (insects such as flies and mosquitos) and arachnids (fleas, mites, spiders, ticks) cause vector-borne diseases that result in misery, illness, and often death. Mosquitos carry and spread an array of parasites and viruses that cause diseases featured in tropical medicine textbooks: malaria, dengue, yellow fever, West Nile, Japanese encephalitis, chikungunya, Zika, and more. As the planet warms and the global climate changes, however, many of the vectors, and thus, the diseases, are now migrating toward more temperate regions of the globe. Tick-borne diseases like Lyme disease are also on the move. The Centers for Disease Control and Prevention recently reported that in the United States, vector-borne diseases are on the rise. Most of the increase comes from ticks (77%) and mosquitos, reports Alexandra Sifferlin:

In the United States, diseases spread by mosquito, flea and tick bites tripled from 2004 to 2016, federal health officials say in a new report. During that time, there were more than 640,000 cases of vector-borne diseases.

“People really do need to take this seriously,” says Dr. Lyle Petersen, the director of the Division of Vector-Borne Diseases in the National Center for Emerging and Zoonotic Infectious Diseases at the Centers for Disease Control and Prevention (CDC)…

“The data show that we’re seeing a steady increase and spread of tick-borne diseases, and an accelerating trend of mosquito-borne diseases introduced from other parts of the world,” says Petersen. “We need to support state and local health agencies responsible for detecting and responding to these diseases and controlling the mosquitoes, ticks and fleas that spread them.”


One of the most effective tools we have in preventing bites and diseases from these critters is also one of the safest. N,N-diethyl-3-methylbenzamide, better known as DEET, has been commercially available in many different bug repellent sprays and lotions for more than 60 years. Markham Heid explains the interesting way in which DEET works:

DEET seems to work by binding to CO2 receptors in the nose-like appendage a mosquito uses to probe a person’s skin for blood, [professor Jonathan] Day says. Rather than kill the mosquito, DEET somehow blocks the insect’s ability to feed. “It works on contact—not on smell—so mosquitos will still land on you but they won’t bite,” he explains. (DEET seems to work in a similar fashion on ticks, although the exact mechanisms by which DEET repels bugs is a point of debate among researchers.)


Even though DEET somehow acquired a scary reputation from a few “scattered research reports tying DEET to health concerns” — parents in particular frequently worry about applying it safely on their children — most research repeatedly demonstrates efficacy AND safety:

Day calls DEET the gold standard of repellants, and one that is nearly always harmless when applied appropriately. “It is very safe,” he says. “Some people are sensitive and may have a skin reaction”—which could include an itchy or swollen rash—”but it’s not harmful otherwise.”

“There are no significant health risks when using DEET repellents in the general population, either [in] adults or children,” says Jeffrey Bloomquist, a professor of insecticide toxicology at Florida.


To apply DEET-containing bug repellents safely:

> Use in an open area that is well-ventilated.

> Spray onto hands first and then rub onto parts of the body that bugs are fond of (ankles, hands, arms, neck, face).

> Parents should apply repellent rather than letting kids apply it themselves in order to prevent inhalation, ingestion, and eye irritation.

> Don’t apply DEET to damaged/injured skin.

> Wash off chemical bug repellents after coming indoors.


Finally, different commercial formulations of bug repellents may have different percentages of DEET as the active ingredient. This is important, says Heid:

Finally, understand that the percentage of DEET a product contains—usually somewhere between 5% and 30%—affects the length of time it will keep bugs away, not how potent or effective it will be. “A 7% DEET will give you about 90 minutes of protection, and you can always reapply it as needed,” Day says. A 30% product, he says, will last up to 10 hours.


With Lyme disease on the rise and mosquito-carrying diseases spreading poleward, it is good to know that DEET will protect us without making us sick.


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