If you feel as if every mosquito has you locked in its sights, while your friends rarely get bit, you’ll want to know why. Jane Clyde consults Dr Yau of DB Medical Centre.
Do mosquitoes find some people tastier than others? The short answer is yes. Female mosquitoes (males do not bite people) need human blood to develop fertile eggs and, according to Dr Yau of DB Medical Centre, they are fussy eaters. “Mosquitoes are twice as likely to prey on people with Type O blood as they are on those with Type A blood,” he says. “Type B blood falls somewhere in the middle.
“Genetics determine many of the factors which attract or repel mosquitoes to our skin,” Dr Yau adds. “Mosquitoes are seemingly attracted by compounds and odours exuded in sweat (lactic acid, uric acid and ammonia), by bacteria on the skin, and high body temperatures.”
Research coming out of the University of Florida suggests mosquitoes like to munch on people with high concentrations of steroids or cholesterol on their skin. “That doesn’t necessarily mean mosquitoes prey on people with higher overall levels of cholesterol; these people simply may be more efficient at processing cholesterol, the by-products of which remain on the skin’s surface,” Dr Yau explains.
Carbon dioxide lures mosquitoes, even over a long distance (up to 50 metres), according to the American Mosquito Control Association (AMCA). “Larger people tend to give off more carbon dioxide, which is why mosquitoes typically target adults rather than small children,” confirms Dr Yau. “Pregnant women (and athletes) are also at increased risk, as they exhale a greater-than-normal amount of carbon dioxide.”
Don’t bug me
Research into mosquitoes’ preferences is just beginning to scratch the surface, and many of the studies coming out, while not medically proven, do seem plausible. For instance, the AMCA reports that wearing dark-coloured clothing increases your risk of getting bit, as does drinking beer and having smelly feet!
While the AMCA suggests that mosquitoes are 500 times more active when the moon is full, Dr Yau can confirm that the highest risk times for mosquito bites are dusk and dawn. “At these times, wind speeds are generally calm, which helps mosquitoes accurately find blood hosts by following scent cues,” he says. “Being small and spindly, they can desiccate in direct sunlight, so they prefer ‘shady’ times of day. By flying at dawn and dusk, they also avoid predators. Birds are going to sleep, and bats are just waking up.”
Asked for some tips on keeping mosquitoes at bay, Dr Yau has this to say. “If considering effectiveness alone, DEET is still the gold standard. A repellent containing a 20% concentration of DEET will give about five hours’ protection. But this has to be balanced with safety concerns: DEET is strong stuff and can damage man-made fabrics. Repellents like Picaridin or lemon eucalyptus oil are less potent but only effective for about one hour. For children under two, I’d recommend a natural repellent containing 2% soybean oil.”
There are many mosquito-fighting methods Dr Yau considers ineffective. These include sound-emitting/ ultrasonic/ electrocuting devices, citronella-soaked wrist, ankle or neck bands, and eating garlic or thiamine. “Stress,” he says, “seems to produce chemicals that repel mosquitoes, and a lucky few of us give off natural repellents.”
You can contact Dr Yau at DB Medical Centre on 2987 5633.