Office of Medical Communications

Joseph Kennedy, M.D., assistant professor of emergency medicine, associate program director of the emergency medicine residency, and director of toxicology education

(AUGUST 27, 2024) Joseph Kennedy, M.D., assistant professor of emergency medicine, associate program director of the emergency medicine residency, and director of toxicology education, spoke with the New York Times about people’s concerns about the effect of DEET bug spray on human health.

DEET’s offensive odor might be its most harmful effect, Kennedy said. Still, there’s widespread concern that DEET might be potentially toxic or cause cancer, he said, with “so many misperceptions.”

Contrary to what many people may think, DEET is not an insecticide, he explained. It doesn’t kill mosquitoes and is not poisonous to them; instead, it simply deters them, likely with its noxious smell.

“The whole point of smelling unpleasant is you’re not the only one that thinks that,” Kennedy said. “Insects do, too,” he said. That includes other bugs like ticks, fleas, and biting flies.

Most incidents the Environmental Protection Agency (EPA) noted were minor, involving skin, eye, or respiratory irritation like rashes, watery eyes, or wheezing. “If you get it in your eyes or your mouth, it is really unpleasant,” Kennedy said.

If used improperly, such as if someone swallows it or applies too much, DEET can cause severe health effects like seizures, low blood pressure, uncoordinated movements, or death, Kennedy said. But those cases are rare.

One major benefit of DEET is its ability to protect against insects that may transmit potentially deadly illnesses like dengue, West Nile, or Lyme disease.

“It’s stunningly effective,” Kennedy said.

When using any chemical, there are risks and benefits. But the toxic side effects of DEET are far less common than what can occur with insect-borne illnesses, such as an irregular heartbeat caused by Lyme disease or severe anemia with tick-borne babesiosis, Kennedy said. “These truly life-altering diseases can be prevented with just some basic precaution and application of a repellent.