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Evidence for dangers of repellent DEET in question

Evidence for dangers of repellent DEET in question
03 Jun 2014

The benefits of avoiding disease-spreading insect bites outweighs the potential risks of using DEET, according to a review of the evidence in the open access journal Parasites and Vectors.

The review looked at a range of studies on the safety of using DEET, including animal research, case reports and other safety assessments, and reached the conclusion that there is no evidence of severe adverse events associated with recommended DEET use.

The authors say that it is important for holidaymakers to protect themselves from the risks of tropical disease by preventing insect bites in the first place, using effective repellents like DEET. This paper is published to coincide with the launch of Bug off - an Insect Repellent Awareness Day. Please see notes for editors for details.

Dr James Logan, Director of arctec at the London School of Hygiene & Tropical Medicine says: "If DEET products are restricted to just 15%, it is likely that millions of people will be put at greater risk of mosquito bites which will dramatically increase their likelihood of developing a disease like malaria or dengue as a result. There is plenty of evidence to show that low levels of DEET are not very effective, so it is important that travellers have access to repellents with greater levels of DEET that will provide the best protection."

DEET is an abbreviation for N,N-diethyl-m-toluamide, which was developed by the US army for jungle warfare just after World War II. It's now the active ingredient in many commercial topical repellents, and is widely accepted by scientists as the most effective known repellent to prevent insect bites which can transmit dangerous diseases like malaria and dengue. However, some governments limit the concentration of DEET in repellents, due to safety concerns after reports of encephalopathy (brain disease) following DEET use.

The researchers reviewed the scientific evidence on the safety of DEET use and found that there was insufficient evidence for risks in humans. Their search discovered only one existing human trial on the safety of DEET, in pregnant women in Thailand. This study compared women who used a DEET-based repellent to prevent malaria transmission to a control group. There was evidence of traces of DEET in the children, suggesting that the substance could cross the placental barrier, but, crucially, no differences in the health of the babies between the DEET treatment group and the control group babies.

The review also looked at existing animal studies to assess the safest amount of DEET to use in repellents and found that insufficient evidence had been gained from these to justify any imposed limits on concentration of DEET. Based on this, the authors weigh the safety risks found in trials against the protection that DEET-based repellents give against transmission of diseases.

Dr Logan says: "Our review article found very few studies that suggested any adverse effect of DEET. In fact, there were only 14 cases of encephalopathy associated with DEET which is extremely small considering the estimated 200 million applications of DEET to the skin each year. If DEET caused serious health problems, we would know about it by now."


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Notes to Editor

1. Assessment of methods used to determine the safety of the topical insect repellent N,N-diethyl-m-toluamide (DEET): a critical review.
Vanessa Chen-Hussey, Ron Behrens and James G Logan
Parasites & Vectors 2014 7:173

Article available at journal website here.

Please name the journal in any story you write. If you are writing for the web, please link to the article. All articles are available free of charge, according to BioMed Central's open access policy.

2. Parasites & Vectors ( is an open access, peer-reviewed online journal dealing with the biology of parasites, parasitic diseases, intermediate hosts, vectors and vector-borne pathogens. Manuscripts published in this journal will be available to all worldwide, with no barriers to access, immediately following acceptance. However, authors retain the copyright of their material and may use it, or distribute it, as they wish.

3. BioMed Central is an STM (Science, Technology and Medicine) publisher which has pioneered the open access publishing model. All peer-reviewed research articles published by BioMed Central are made immediately and freely accessible online, and are licensed to allow redistribution and reuse. BioMed Central is part of Springer Science+Business Media, a leading global publisher in the STM sector.

4. Insect Repellent Awareness Day is launched by the scientists from repellent testing facility arctec at the London School of Hygiene & Tropical Medicine on 3rd June 2014. The Bug Off campaign aims to highlight the importance of using insect repellents and to dispel the many myths and misconceptions about how to repel mosquitoes and other biting insects which can leave people at risk of harm to their health. It is also running an educational outreach programme, including school visits and a poster competition which opens today.

More information, including a downloadable version of the schools resources and poster competition, will be available at

Please click on the link(s) provided.

ResearchArticle_Assessment of methods used to determine the safety of the topical insect repellent N,N-diethyl-m-toluamide (DEET).pdf

NewsRelease_Evidence for dangers of the repellent DEET in question.pdf

For further information, please reply to Anna Perman