![Credit: [Oxbow Park Naturalization Project].](http://scienceline.org/_s/files/2007/09/mosquito.jpg)
ask scienceline | health | biology | environment
Why do mosquitoes bite some people more than others?
- asks Allison from Austin
Every summer, they come. They sneak through the windows and ravage your ankles; they find the one spot on your left shoulder that didn’t get drenched in a layer of DEET (God bless you, Deep Woods Off!) and gnaw, chomp, and suck away.
From May to September, many of us – covered in scars and bloody scabs, the remnants of these bites now gone bad – live side-by-side with people who, despite living in the same house and even sleeping in the same bed, are seemingly less vulnerable to the vicious six-legged predators. It turns out, a mosquito’s snacking preference for one person over another is not just a curious annoyance, it’s also a medical concern: Since malaria and other diseases are transmitted by bites, people who get bitten a lot are more likely to become ill. Because of this, researchers are working to find the mechanisms in mosquitoes that cause them to sniff out you, and not your neighbor.
Scientists have identified several proteins found in mosquitoes’ antennae and heads that latch on to chemical markers, or odorants, emitted from our skin. These markers are produced by the natural processes of our bodies and, like neon signs, they let the mosquitoes’ smell center know you’re around (though the process that then guides them to you is not well understood). Flies and mosquitoes share a number of the same genes that dictate production of these odorant-binding proteins, which have specific sites that will catch or bind with certain chemicals in the air. Some scientists suggest that certain characteristics attract mosquitoes, thereby leading us to have more bites than others. Some of the top candidates: the amount of carbon dioxide in the breath, pregnancy, body temperature, alcohol and odorant markers based on blood type.
Blood-type markers are chemicals released by people of a specific blood type – so if someone with AB blood emitted a marker, it would be different than that released by B. One study found persons with Type O blood suffered more mosquito landings because of the odorant markers they emit than any other blood type, making their juices a hot commodity for blood banks, as well as Asian Tiger Mosquitoes, which carry West Nile Virus. Not only were Type O’s more likely to be landed on, but the study found that for any blood type, people who secreted a chemical marker about their blood type through their skin (both blood type and secretor status are determined by genes) were bitten much more than non-secretors; 24 percent in the case of the Type O’s. Other researchers estimate about 15 percent of the population, based on their genes, don’t emit chemical markers of their blood type through their skin and saliva, so something else has to be calling the mosquitoes to them.
Pregnancy seems to be a big winner for mosquito attraction, probably because mothers-to-be exhale 21 percent more carbon dioxide (quite a turn-on to the six-legged species) and are on average 1.26 degrees Fahrenheit warmer around the belly than their non-pregnant counterparts, due to the temperature of amniotic fluid. Also, having just 12 ounces of beer increases your mosquito appeal, possibly because of the increase in body temperature it causes or because skin markers change when metabolizing cocktails – unfortunate since outdoor drinking is a highlight of summer anywhere.
One researcher suggested smell is unimportant, and what really matters to the mosquito currently chomping on your toe is not the smells you’re giving off, rather it’s finishing her meal without being swatted away. Because of this, she’s better off attacking “less defensive” animals, rather than more defensive, and so is evolutionarily predisposed to biting lazy or incapacitated prey (reference drinking above).
Infectious disease experts are anxious to solve the mosquito preference puzzle so they can design repellants tailored to vulnerable people, which would either block an individual’s smell signatures or disarm a mosquito’s scent receptors. Unfortunately, a specific answer to your skin-piercing question continues to itch away at scientists, and I suggest stocking up on bug repellant in the meantime.
May 26th, 2008 at 12:17 am
thank you for the article.now i can answer to some dumb people when they say i get bit by mosquitoes because of my body smell.i get so agravated!!!
July 17th, 2008 at 6:49 pm
I just absolutely KNEW that frequency of bites had to do with blood type. I am type O and am ALWAYS getting eaten alive by mosquitos! Many of my friends that are type A NEVER get bitten, even when a mosquito lands on them!
July 20th, 2008 at 9:57 am
Erm… I’m an O and I never get bitten!!
July 21st, 2008 at 1:24 am
My blood type is a+ and I am always getting bitten. I think it’s because I am so sweet. LOL
July 23rd, 2008 at 9:17 pm
I have a real problem with mosquitoes biting at my bag, is it possible my bag emits an odor that attracts mosquitoes?
LOL this thread is messed. Mosquitoes bite people to live and feed their young, the numbers mean nothing and I would have to go with the chaos theory, in that someone has to be bit more than another and someone has to be bit less, otherwise the world would explode without randomness, or chaos.
Wanna learn something that pertains to everything, check out chaos theory. Stats are pointless.
July 24th, 2008 at 9:46 pm
Interesting, but my family totally blows the blood type theory. I have a daughter who is B+ who absolutely gets eaten alive and one who is A+ with a pretty strong attreaction. The rest of us who are A+ and O+ use the first two as our repellent.
August 1st, 2008 at 5:23 am
Last year i went on holiday, my brother aged 10 and my son aged 4 shared the same room my brother got bitten loads with repellent on and yet my son didn’t get one bite we used repellent on him the first couple of days, but after that he didn’t have any on as they didn’t seem to like him and he still didn’t get bitten. Im just intriged to know why???
August 1st, 2008 at 12:55 pm
Always knew it must be linked to blood type, not sure on the O type though, Im A- and always get bitten alive while no-one else does!!???
August 6th, 2008 at 12:23 pm
Thank you for this article. now i have an answer to why mosquitoes bite me all the time instead of the other people in the same room as me. it’s only because of my rich thick blood type! and because of bodyly secretions that i give off. and my smell, and a whole lot of other things. thanks!
August 8th, 2008 at 3:55 am
how about this…when i get bit by mosquitoes, which not only seems to be more than everyone i know, i get bitten in quick clusters. i don’t just get one generic bite here and there. i will get bit in repeated succession in a big cluster of sometimes four or five bites in a small area. no matter where i go, this holds true.
August 18th, 2008 at 2:29 pm
i am type O and i never get bit. i don’t think i’m buying the blood type theory. there are posts here of people all over the blood type spectrum and their experiences are just as widely ranged.
August 31st, 2008 at 12:48 am
OMGGGGGG!!!!!!!!!!!!!!!!!
I GET BITTEN BY mosquito all the time, and i have no idea what my blood type is.
September 2nd, 2008 at 11:00 am
I am type O and get eaten alive even with repellant on. I also have a blood disease called ITP, and I wonder if they like me because my blood does not clot normally.
September 6th, 2008 at 1:31 pm
Interesting…but the photo above the article is not that of a mosquito but a (harmless) crane fly. it would be hard to bite someone, regardless of blood type, without a nice long proboscis (nasty bitey part).
September 15th, 2008 at 10:55 am
I am blood type B+ and have been attacked by mosquitoes continuously all of my 70 plus years. I have applied many different types of repellants but as of yet have not found one that works well. I have attracted them in the American continent all areas and also in Asia. I am resigned to being bit as there isn’t much I can do about it, hopefully sience will discover the reason and develope a repellant.
September 17th, 2008 at 1:43 pm
This information I just read is right. I have never been bitten by mosquitoes But now i have been drinking a couple of beers in the afternoon and I go out and i get bitten within minutes at least in four different places uncles ,elbows and ,knees .When I drank red wine it never happen
September 17th, 2008 at 10:11 pm
I am AB+ blood type and Im bitten by mosquitos ALL THE TIME! Im just so sick of it!! Even the repellants dont help me! Its terrible.
However, besides the blood type, the article states that the body warmth and alcohoc composition are also factors of attraction! :(
Thank you for the article!
September 25th, 2008 at 8:58 pm
blood type? what about body temperature? I have a normal body temporature of 96.3sih rather then 98.6 and i never seem to get bit. might not this be the major factor? warmer people get bit and cooler people don’t….Possible?
September 29th, 2008 at 9:45 pm
One thing the article mentioned is that not everyone emits the scent of their blood type. Which would explain why some people with a certain blood type get bitten and some don’t - they don’t excrete the scent.
I get bitten constantly. My mom does too. On a recent vacation to a lake house I was outside just as frequently as 2 friends and my husband (who threatened to put me in a bubble!) - we all drank the same amount, wore bug spray, and were even using the same shampoo and soap. I went in every night covered in bites, while everyone else was untouched; including, luckily, my son.
It is obnoxious. We just killed one in the house - it bit me 5 times before we could get it. Grrr…
Body temp is interesting - I have a low body temperature of around 96.7, and I don’t remember bites being much of a problem when I was pregnant.
Thanks for the article!
October 7th, 2008 at 8:00 am
I live in a hot country and being constantly bitten is getting me down quite a lot.
I now wear repellent every day and carry it with me. When i arrived 3 months ago i ended up scratching so much that the bumps and itching came up all over my arms and legs and stomach. It seemed like an allergic reaction to the bites but the doctor didn’t seem sure what had caused it. She said it was a food allergy or an allergic reaction to the bites. I think it was the latter.
I have A type blood so that blood theory seems a bit off to me. My partner doesn’t get bitten very often, just now and then. Also my daughter gets quite a lot but not my son. Is it the female hormones that maybe attract them more or what?? The biggest annoyance is that i’ve been wearing trousers lately and get bitten on my legs so how the heck are they getting up my legs. I despise mosquitos. Why can’t they become extinct??
October 8th, 2008 at 2:14 am
I’m type O and used to get bitten a lot. Now that i’m older, i don’t get bitten as much. As it’s stated, 15 percent don’t emit the blood marker. But from what i’ve learnt, mosquitos are attracted to CO2 as well. So people that never get bit either don’t emit much CO2 or a blood marker or are move enough to keep them off.
It states that type O are bitten more, but that could be the marker is more familiar as there’s more O around and is the oldest type.
People that aren’t O but get bitten a lot, it could be you give off more CO2, emitted a higher blood marker or just really unlucky. I think i get bitten less because i weigh a lot more and my diet’s changed.