DEET Mosquito Repellent Seemed Safe

DEET insect repellent appeared to have no negative effects

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) Summertime brings sunshine and warmth, but also those pesky mosquitos and attempts to ward them off. Many people might wonder whether insect repellents with DEET are safe.

DEET stands for "N,N-diethyl-m-toluamide," a compound shown to be effective in warding off insects.

A recent study found no evidence of negative health side effects related to the use of DEET at the recommended levels.

In countries where disease-carrying mosquitoes are a risk, repellents with 20 to 50 percent DEET are recommended.

"Take steps to prevent mosquito bites."

This study, led by Vanessa Chen-Hussey, of the Department of Disease Control at the London School of Hygiene & Tropical Medicine in the United Kingdom, assessed the methods that have been used to determine the safety of DEET.

The authors reviewed animal studies, observational studies and studies in which one group was exposed to DEET and another group was not.

The researchers did find evidence of minor adverse effects in animal studies, but these only occurred with extremely high doses of DEET.

Those effects also did not show up in further studies across different species, so those findings could not be applied to humans.

There were no human studies designed specifically to assess DEET.

However, one randomized, controlled trial on humans looking at malaria prevention measures compared a group of pregnant women in Thailand who were exposed to DEET to another group of pregnant Thai women not exposed to DEET. This trial found no differences in neurological outcomes, death or physical characteristics at birth through one year between the two groups.

That study and another in New Jersey determined through cord blood samples that DEET did cross the placenta, but neither study found negative effects from it.

The authors noted that the risk of DEET is, so far, a theoretical risk that lacks evidence. Yet the possible harms of not taking measures to prevent insect bites can be severe, especially in parts of the country or the world where mosquitoes carry deadly diseases.

West Nile virus is among the diseases carried by mosquitoes in some parts of the US, and recent reports in the past year have found some dengue fever-carrying mosquitoes in parts of the southern US.

In other parts of the world, malaria, dengue fever, yellow fever and a parasitic disease called filariasis have far more severe effects than the hypothetical effects of DEET.

Anyone visiting countries where these diseases exist, including popular tropical destinations, should take precautions to reduce the risk of being bitten by mosquitoes, the authors advised.

In countries with serious disease-carrying mosquitoes, the authors recommend using insect repellents with 20 to 50 percent DEET.

Even when the risk of disease from mosquitoes is low, infections can result from the scratching caused by mosquito bites.

No evidence has shown that diet changes, such as eating garlic, will prevent biting.

This study was published June 3 in the journal Parasites and Vectors. Funding information for the study was not provided.

One author is the director and another a research scientist at the the Arthropod Control Product Test Centre at the London School of Hygiene & Tropical Medicine, which provides impartial commercial testing services on insect repellent effectiveness.

Review Date: 
June 6, 2014
Last Updated:
June 9, 2014