There is a joke among abortion proponents that if men could get pregnant, abortion clinics would be more common on city streets than Starbucks coffee shops. If that is so, the best way to get something done about insects in developing nations would be to send environmentalists there.  Sitting in cozy western offices, it is easy to rail against DDT and genetic modification but the first time a Union of Concerned Scientists fundraiser gets dengue fever they would be all for science solutions to mosquitoes.

Of course, that will never happen, it is easier to do important work criticizing science from a distance. But eco-tourism is big business and there are plenty of good reasons it will help the environment - large influxes of money and fees can fix a lot of problems. But if you go to a poor tropical country you'd better bring insect repellent. Dengue is the most common "vector-borne" (result of feeding activity) disease in the world, with 2.5 billion people at risk, and you don't want to be one of them.

With the World Cup about to begin in Brazil, local officials are going to encourage tourists not to deviate more than four square miles from their hotels and to just appreciate the culture really close by. That is smart thinking, primarily for crime, but also for general health. While westerners getting Dengue fever would get action taken, it probably isn't a sacrifice you personally want to make. And so scientists from repellent testing facility arctec at the London School of Hygiene&Tropical Medicine have launched Bug Off - the first ever Insect Repellent Awareness Day to, well, bring awareness to people who apparently don't think they need insect repellent in third world countries. 

They recommend applying repellents containing 20-50% DEET to the skin when in countries with diseases spread by insects, such as malaria and dengue fever. 

What about the safety of DEET? It's been primarily another fundraising claim manufactured by activists but just to be sure,  the scientists behind Bug Off conducted a review of published studies and couldn't find (meaningful) evidence that DEET is unsafe. Someone is always drowning insects in bug spray and declaring that could harm people but that doesn't count. Hypothetical posturing by people trying to raise money creating scary chemical stories is a much different proposition than actually getting malaria.   

The processes involved in creating a safe exposure assessment of any chemical. Link and credit:


In their analysis of animal research and other safety assessments carried out previously, the School researchers conclude that there is no evidence of association between severe adverse events and recommended DEET use. They also looked at case reports of people suffering encephalopathy (brain condition) following exposure to DEET in the 1980s. The researchers state that, even when allowing for underreporting, "the incidence of 14 reported cases of DEET-associated encephalopathy since 1957 is small when considered against the context of an estimated 200 million applications of DEET worldwide each year."

According to separate analysis by experts from the School of overseas travel, the number of visits by Britons to tropical countries went up almost 50 percent between 2002 and 2012, 4.02 million to 6.03 million.

Since there is no cure and no vaccine against Dengue fever, and a whole lot of people will be visiting Brazil, repellents are the number one protection. Fortunately, it is winter in Brazil, which means the risk is lower in most areas but football fans traveling to the country are still advised to apply effective repellent frequently.  

Key facts on insect repellents:

  • If you are traveling to countries with diseases spread by insects then using insect repellents containing DEET is recommended. 

  • DEET – a repellent applied to the skin to repel biting insects - should not be confused with DDT, which is an insecticide designed to kill insects.

  • There is no evidence that changes in diet, for example eating marmite or garlic, will prevent biting.

  • Repellents wear off in time and need to be reapplied, especially in warm climates and during activities that involve a lot of movement.

  • Preventing biting is not only important against disease, but nuisance biting even in the UK can lead to infections due to scratching.

Dr. James Logan, Senior Lecturer in Medical Entomology at the London School of Hygiene&Tropical Medicine and Director of arctec, said, "Biting arthropods can transmit a whole range of diseases to humans and it is vital to protect ourselves. Vaccines and treatments are available for some diseases but not all and so the best way to keep as safe as possible is to use an insect repellent containing DEET and reapply it regularly.

"We want people to enjoy their holidays and tropical trips – we don't want them ruined by illness so we want to do all we can to help inform and educate people about the facts rather than the many myths surrounding this issue."

Dr. Ron Behrens, Consultant in Travel Medicine and Senior Lecturer at the London School of Hygiene & Tropical Medicine, said, "Travelers often underestimate the need for and application of repellents. I always encourage them to take along enough supplies of repellent and always carry a bottle with them when out and about to maintain protection throughout the day and evening. 

"If bites do happen, make sure they don't become infected by applying an antiseptic and try to avoid scratching them."

 Citation: Vanessa Chen-Hussey, Ron Behrens, James G Logan, 'Assessment of methods used to determine the safety of the topical insect repellent N,N-diethyl-m-toluamide (DEET)', Parasites & Vectors 2014, 7:173 doi:10.1186/1756-3305-7-173.
Source: London School of Hygiene & Tropical Medicine