The Pharmaceutical Journal
Vol 269 No 7206 p47
13 July 2002

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New England Journal of Medicine (content.nejm.org)

DEET beats other insect repellents in new tests

Insect repellents containing high concentrations of DEET (diethyltoluamide) offer better protection against mosquito bites than products containing the repellent IR3535 (ethyl butylacetylaminoproprionate) or botanical agents such as citronella, a new study has found.

The study involved 15 volunteers who inserted their repellent-treated arms into standardised cages containing a fixed number of unfed mosquitoes.

DEET-based products were found to provide complete protection for the longest time. Higher concentrations of DEET provided longer-lasting protection.

A formulation containing 23.8 per cent DEET had a mean complete protection time of around 300 minutes. A soyabean oil product protected for an average of 95 minutes and the IR3535-based repellent protected for an average of 23 minutes. Botanical repellents, containing citronella with or without other oils, protected for a mean duration of less than 20 minutes. Repellent-impregnated wristbands offered no protection.

The researchers say that non-DEET repellents cannot be relied on to provide prolonged protection where mosquito-borne diseases are a substantial threat (New England Journal of Medicine 2002;347:13).

Legislation on DEET has become increasingly restrictive in some countries, with a ban in Denmark and a maximum concentration being allowed in the Netherlands (PJ, 27 May 2000, p793). Although there have been concerns over the toxic effects of DEET, particularly skin reactions, the British National Formulary (Number 43, p299) says that DEET is "safe and effective when applied to the skin".