Almost everyone has that one friend who is the first to get awfully itchy bug bites when they are having an outdoor hangout in the evening. Yeah, that friend who repeatedly stamps their feet in frustration and says, “there are mosquitoes here!” The reaction is often a collective “you’re exaggerating this’ stare from the other members of the clique. What you don’t know is, that friend of yours has some special attraction for mosquitoes and people like them have been collectively referred to as mosquito magnets by scientists.
A recently completed study carried out by researchers from Rockefeller University revealed that humans are either “mosquito magnets” or “low attractors” of the insect. By examining skin secretions from 64 volunteers over a timeframe of 3 years, they were able to establish that some people are naturally high attractors of mosquitoes. This research was conducted by Professor Leslie Vosshall and her team. They made volunteers wear plastic stockings for about 6 hours per day, several days a week, for months or even spanning years. These stockings were placed in chambers and yellow-fever-causing mosquitoes were introduced into the chambers. They observed that the mosquitoes trooped to certain stockings compared to others.
On careful analysis of the skin secretions found in the stockings which mosquitoes were most attracted to, they found 50 molecular compounds that entice these insects. On the skin of mosquito magnets, these natural substances were higher in secretion compared to other volunteers were discovered. However, the most distinguishing factor for the two groups was the higher rates of carboxylic acid found on the skin of mosquito magnets compared to their counterparts who were low attractors. Does this mean carboxylic acid is dangerous or harmful? Not exactly.
Carboxylic acids are, in fact, a component of a substance called sebum— a natural oil that creates a protective film on our skin and helps keep our bodies well moisturized. Bacteria living on human skin tend to feed on these acids and this ingestion gives off what we smell when a human is around. This means that with more carboxylic acids on a person’s skin, mosquitoes quickly detect that a human is right in the corner whether it is dark or not. Although scientists are yet to figure out why mosquitoes are so enticed by carboxylic acids, they believe that both our body heat and the carbon dioxide we exhale are very strong attractions for mosquitoes to humans.
Even though some soaps, creams, and skincare products are known to affect the carboxylic acid levels on the skin, the status of individuals either as mosquito magnets or low attractors remained constant throughout the study whether they changed their body lotions or shower gels. Although most people think mosquitoes only feed on human blood, their females also need blood to fertilize their eggs. This explains the continual evolution and behavioral adaptation that makes control measures seem less efficacious over time in many African nations.
As mosquitoes continue to evolve to find their prey using their olfactory abilities, what then can be done with this new knowledge? Well, trying to get rid of carboxylic acids on the skin of mosquito magnets will have adverse effects on skin health and eventually lead to avoidable skin diseases. Notwithstanding, researchers believe that mosquito repellant manufacturers can use this new discovery to control mosquitoes effectively.
Ehi-kowoicho Ogwiji is a storyteller and natural scientist who is given to advocacy for a science-literate Africa. Ehi-kowoicho aspires to be a renowned science communicator and STEM thought leader in Africa and beyond. She writes from Abuja, Nigeria. Connect with her on social media @ogwijiehi or email her at [email protected]