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In recent years there has been considerable debate about DEET (diethyltoluamide), the active ingredient used in most insect repellents. This synthetic chemical was developed by the US government in 1951 after testing 11,000 compounds for their effectiveness in repelling insects, and no other substance has been found to be more effective. Today, DEET is the most widely used and the most powerful repellent in the world, used by an estimated 200 million people worldwide each year.
Numerous studies have been carried out to determine whether DEET-containing repellents could be harmful to human health and no serious adverse effects have been found either to people or to the environment when the products are used properly. If incorrectly used (e.g. swallowed) DEET based products are toxic and can lead to acute poisoning. As with any other household chemicals, repellents with DEET should be stored away from children.
Health concerns relate to the fact that many chemical repellents are absorbed through the skin into the blood and reappear in the urine, unchanged, hours later. As with any topically applied product, local reactions can occur when applied to the skin, particularly at high doses. This generally results in no more than a rash or itching but in a small percentage of people it can result in more serious medical complications - although these are usually associated with inappropriate use such as applying excessive amounts, swallowing it, or spraying it into the eyes. Consequently, DEET should always be used sparingly and application to infants and young children is not recommended.
Users should also be aware that the active ingredient in DEET is a plastic solvent, which can damage items such as spectacle frames, watches, wood finishes and many synthetic materials. Users should protect their belongings from coming into contact with DEET products by washing their hands after each application.
If there are potential risks attached to DEET, the same is true for many insect bites, which can cause serious health problems. Some people develop a severe sensitivity to being bitten, bites can become infected and they can even lead to life-threatening diseases. Malaria is the most important disease spread by mosquitoes killing millions every year, while annually several thousand tourists return home to the UK with the disease.
As such, it is critical for the holidaymaker that the most effective protection is used. But what is the optimum level? Numerous studies over the 40 years since DEET was introduced show that the level and duration of protection increases with the level of DEET concentration. Data also shows that the rate of absorption is lower with the higher levels of DEET than with lower concentrations formulated in alcohol. Despite some recent views that 50% DEET may be as efficacious as higher concentrations of DEET, the scientific data demonstrates that this is just not the case. The amount to use rests on the level of risk in the area to be visited and if the risk is high, a high DEET concentration is advised.
It seems that the DEET dilemma boils down to relative risk - using DEET may present some health concerns but being bitten by certain types of insect may also be dangerous to health. Responsible use is the key. Use it as you would any chemical - with common sense.
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