A biting chance

The first signs of spring in the west of Scotland are here, and I've already seen some midges, those blood-sucking insects that can ruin a summer. Not to worry: an urban myth says that Avon's Skin So Soft bath oil is so good at repelling the tiny critters that US marines swear by it, whether stationed off Faslane or in malarious jungles around the world. Avon's sales in Scotland are strong, but does it really work?

Last year, we ran a test. Equal numbers of mosquitoes in net-covered jars were released for 15 minutes among students divided into two groups. One had applied Skin So Soft to their forearm; the other used a proprietary formulation containing DEET (a chemical introduced by the US army in the 1940s). The results were compared to those for a control group that had applied nothing. The untreated group had 143 bites in total. The Skin So Soft group seemed to fare a little better - 119 bites. Those that used DEET had 37 bites.

The DEET formulation worked (it blocks sensory receptors in the insect's antennae so they can't smell where to bite). However, the apparent effect with Skin So Soft was not significant when we applied a statistical test.

It doesn't matter so much in Scotland, but in countries where malaria, yellow fever, plague and many other insect-borne diseases are rampant, it would pay not to rely on an urban myth.