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The truth about mosquito bites – and how to avoid them…

February 21, 2013

Let’s clear up some of the nonsense being talked about today about mosquitoes and the widely used repellent ‘DEET’.

The BBC copy editors are yet again trying to summarize a story with inaccurate strap-lines…


Today’s BBC news story is that researchers have found that individual mosquitoes are initially repelled by DEET (N,N-Diethyl-meta-toluamide), but

“a few hours later when the same mosquitoes were offered a chance to dine again, the researchers found that the Deet was less effective. the same mosquitoes are less repelled by the chemical…”

As is too often the case, a BBC sub-editor has created an misleading strapline for the story on the BBC news website – in this case:

“The widely used insect repellent Deet appears to be losing its effectiveness against mosquitoes, scientists say.”

This confusion continued on Radio 4 “You and Yours”  programme where there was also speculation that ‘local people’ in tropical areas seem less bothered by bites and are ‘immune’.

This is rubbish, of course. Although it is true that the effect of mosquito bites are less obvious, this is just because of less inflammation of the skin due to habitual exposure leading to desensitization to bites. Make no mistake, local people suffer from malaria every bit as much as someone from a temperate zone.


I have worked in India and several African countries, and the correct application of DEET is essential. Let’s make this clear: there is no evidence from today’s report that DEET is losing is effectiveness as a repellant overall. Also, the website article and the Radio 4 programme did not explain that DEET should be applied to clothing not direct onto skin, where it loses potency quickly as it is absorbed into the skin itself.  Put it on your socks, shirt collar and cuffs, and re-apply every 4 hours. In the bush spray it everywhere…

(Handy hint: DEET dissolves many plastics, so avoid getting it on your palms or fingers.  My briefcase stuck to my hand once in Bangalore airport!)

(Handy hint #2: Carry a small DEET container onboard your flight, and apply it liberally before deplaning at your tropical destination. Airports are often built near flat marshy land…)

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