By Ginny A. Roth ~
We’ve all been there. It’s finally time for that fun summer barbecue. You’re surrounded by family and friends, the weather is warm, the burgers are cooking, and nothing can ruin this perfect evening. Well, almost nothing. While you are lying on your deck chair, eyes closed, and having enjoyed your glorious meal, you are suddenly jolted from euphoria by a painful feeling on your arm. Instinctively you smack yourself on the offending spot. Then it happens again. This time on your ankle. Annoyed, you open your eyes and sit-up. There is movement everywhere. Thousands of erratically-flying objects have descended upon you—and only you. None of your guests are affected by this phenomenon. You think for a moment that you may be in a 1950s horror movie. But soon you realize that it’s real… mosquitoes from everywhere, and seemingly out of nowhere, are swarming around you. Your attempt to create an insect barrier is futile: lighting citronella candles on your backyard tables is no match for these beasts who have flown far to satisfy their need for sustenance.
In situations such as this, you may ask yourself, “Why me?” Believe it or not, although it sounds improbable, you may be more attractive to mosquitoes than your friends. According to an article published in Smithsonian Magazine, 20% of the population is especially appealing to mosquitoes in part because of blood type, citing that individuals with Type O blood are the most attractive to mosquitoes. But how do mosquitoes know what blood type you are? Well, they don’t. But they do know if you are a “secretor.” Secretors are individuals who have a gene that allows the body to secrete their blood type antigens into saliva and other body fluids. Mosquitoes are attracted to these secretions, and roughly 80% of the population carry this gene. One 2010 study published in the International Journal of Nanomedicine indicates that those who have Type O blood have a significantly higher frequency of secretor status (as opposed to non-secretor status) than those with other blood types. According to a 2004 study published in the Journal of Medical Entomology, among individuals that are secretors, Aedes albopictus mosquitoes have a higher “landing preference” to those who have blood Type O over other blood types.
Another compelling reason that mosquitoes may like you more than your friends is your body odor. All of us have skin odor emanating from our bodies that is caused by the presence of bacteria. A 2011 study published in PLUS ONE reveals that females of the mosquito species Anopheles, which carries malaria, rate your attractiveness by the amount and diversity of bacteria on your skin. It has also been suggested, as noted in a 2015 study also published in PLUS ONE, that “human odour is known to be controlled, at least in part, by genetic factors, and it is possible that variation in our attractiveness to mosquitoes is also modulated via the same mechanism.”
Unfortunately, you have no control over your genes, your blood type, or, at least in some cases, your body odor. But all is not lost. There are other factors within your control that can diminish your level of mosquito-likeability. Your choice of clothing is one of these factors. The University of Wisconsin’s Entomology Lab reports that dark-colored clothing attracts some species of mosquitoes more than reflective clothing. Wearing lighter colors in the summer is better anyway because it will keep you cool during the hottest days of the year.
If you drink alcohol, that could also increase your chances of being bitten. A 2002 study from the Journal of the American Mosquito Control Association concluded that after humans consume ethanol, mosquitoes become more attracted to them, most likely because of unknown chemical substances that form on the skin after ethanol consumption.
Mosquito bites can be serious, as some of the insects are vectors for diseases. You don’t need to cancel your outdoor plans, but it is prudent to be aware of the dangers that mosquitoes can pose and to know what to do in case you are bitten and when to seek medical attention.
Find more information on efforts to control mosquito-transmitted diseases on Circulating Now: Web Collecting During the Zika Outbreak, Setting Our Sites on a World Without Malaria, and World Malaria Day. You can also check out the National Library of Medicine’s (NLM) online exhibition Against the Odds: Making a Difference in Global Health.
Ginny A. Roth is the Curator of Prints & Photographs in the History of Medicine Division at the National Library of Medicine.