July 26, 2021

I, Science

The science magazine of Imperial College

Being stuck in a dark room with a blood sucking insect is never a pleasant experience. Worse than the high pitch whine that swoops by your ear is the knowledge that you could become an unwilling blood donor at any time.

There are some people however, who never seem to get bitten. What is it about them that make them so inedible?

The answer is seems is on our skin. Our bodies are covered in microorganisms. There are over 150 bacterial species on the average hand palm. If this has prompted you into compulsive hand washing you might want to remember your inner elbow, there’s an average of 88 species there too. Our skin has a complex world of microbiota living on it.

These bacteria produce odour. Without it, our sweat wouldn’t smell of anything. Different species of bacteria have odour profiles. Bacillis subtilis for example is linked to smelly feet. The bacteria on our skin vary from person to person, so the exact composition of odours released will also vary between individuals.  

This is where the mosquito comes in. They track us by our human smell. The odours produced by some bacterial species also attract more mosquitoes than others.

In fact a study published in December  found a clear hierarchy in how attractive skin bacteria odours were to mosquitoes. Right at the top of the list was Corynebacterium minutissimum one of the bacteria present in high numbers on the human foot.

If mosquitoes are more attracted to the odours of particular bacterial species and if humans differ in the composition of bacteria on our bodies, some people’s skin odour will be more attractive to mosquitoes than others.  The insects are more likely to feed off this person when given a choice. Life as they say is unfair.

The mosquito species that is so good at distinguishing between human bacterial odours is also the Anopheles gambiae, the main carrier of Malaria. The relationship between malaria mosquitoes and the humans they feed on is still not completely understood but research like this helps explain why some people get bitten more than others and could mean new methods of disease prevention and control in the future.