DEET, the common name for diethyltoluamide, is the most common active ingredient in insect-repellent sprays, lotions, sticks, roll-ons, and other consumer products. In the U.S., over a third of the population regularly uses DEET-containing products – ranging anywhere from five to 99 percent – according to the U.S. Environmental Protection Agency. It is touted as one of the most effective ways to prevent vector-borne diseases, which are caused by parasites, viruses, and bacteria transmitted by insects – mosquitoes, sandflies, and lice – and snails. Vector-borne diseases account for around 17 percent of all infectious diseases reported worldwide. Every year, over 700,000 deaths are caused by vector diseases, with malaria causing more than half of these cases.
Initially developed in the 1940s by the U.S. Army to protect soldiers in bug-infested areas, DEET was introduced to the public in the late-1950s and is now a key ingredient in over 120 products. However, recent studies about the potential health risks of synthetic repellents and pesticides like DEET raised awareness to more potent and longer lasting natural alternatives.
The study, led by Jerry Zhu of the ARS Agroecosystem Management Research Unit in Nebraska, found that coconut fatty acids repelled bed bugs and biting flies for two weeks after application. The result was better than that of DEET, which only lasted for around three days before losing its effectiveness. It was also effective against ticks, with laboratory tests showing that it can repel ticks for a week after application, and mosquitoes, with coconut oil compounds exhibiting a concentration-dependent effect when applied to the skin.
The compounds were also effective on animals. In field trials, the researchers noted that a starch-based formula containing coconut oil fatty acids protected cattle against stable flies for up to 96 hours (four days). In comparison, DEET was only 50 percent effective against stable flies.
'To our knowledge, this is also the first report showing that the longevity and effectiveness of these natural repellent compounds better than the gold standard repellent, DEET against those blood-sucking insects," they wrote in their report.
Most DEET products are designed for direct application to the skin, allowing it to create a barrier that masks human scent from insects. While it may be effective at repelling insects, as multiple studies found, it's worth noting that there is mounting evidence about its potential side effects.
A study in the late 1980s found that subjects from the Everglades National Park reported negative effects from exposure to DEET. Some of the effects included rashes, skin irritation, numb or burning lips, nausea, dizziness, headaches, and difficulty concentrating.
Another study, this time from Duke University pharmacologist Mohamed Abou-Donia, found that prolonged DEET exposure caused brain cell death and behavioral changes, based on rat models. Yet, more research shows that DEET exposure is linked to immune system suppression, transgenerational disease inheritance, and sperm mutation, based on animal studies. (Related: Chemical Mosquito Repellant DEET Causes Neurological Damage, Gets Absorbed Through The Skin.)
There have been cases of people reporting side effects after being exposed to DEET. The symptoms that they reported ranged from pruritus (extreme itchiness), erythema (redness of the skin), and severe hives. A study published in the International Journal of Toxicology in 2002 found that over 20,000 cases of DEET-related cases were reported to poison control centers from 1993 to 1997, where two casualties were reported, and 26 patients experienced significant side effects.