Why is it that when you go on holiday some members of your family always seem to get bitten more than others?Researchers supported by the Biotechnology and Biological Sciences Research Council (BBSRC) think they may have found the answer and their work could lead to new types of insect repellent.

　　James Logan, a research student at the BBSRC-sponsored institute Rothamsted Research in Hertfordshire, has found that some people give off "masking" odours that prevent mosquitoes from finding them. His research builds on earlier studies on cattle at Rothamsted Research, led by Professor John Pickett, which showed that the number of flies on a herd depended on certain cows being present. The scientists found these key unattractive individuals gave out different chemical signals from the other cows. When these individuals were moved to another field the number of flies afflicting the herd increased.

　　James, working in collaboration with Professor Jenny Mordue at the University of Aberdeen, tested the behavioural reaction of yellow fever mosquitoes to the odour of the volunteers. James said: "The mosquitoes were placed into a y-shaped tube and given the choice of moving upwind down either branch. The air flowing down one branch was laced with odour from the volunteer's hands."

　　Their results suggest that differential attractiveness is due to compounds in unattractive individuals that switch off attraction either by acting as repellents or by masking the attractant components of human odour. This theory differs from that of other research groups who have suggested that unattractive individuals lack the attractive components. The researchers are now testing these theories further using foil sleeping bags to collect whole body odours from volunteers.

　　Professor Julia Goodfellow, BBSRC Chief Executive, said, "There are clear benefits from this research. Discovering what makes a person more attractive to mosquitoes presents scientists with the opportunity to develop safe, naturally occurring insect repellent which could be far more effective than conventional products because it relates to the way mosquitoes select their hosts." James said, "By identifying these key components and understanding how they work we could be closer to new methods of protection from these biting pests that cause losses in livestock and irritation and illness in humans."