I spend a lot of time outdoors and over time have definitely noticed
that some people are more susceptible to mosquito bites than others. 
For example, I was out mountain biking yesterday with a group of five
people.  We sat down at one point to eat lunch.  Mosquitoes were
swarming around one woman while leaving everyone else alone.  This
woman mentioned that mosquitoes have always been particularly
attracked to her.  Another example is when I went hiking with a friend
of mine.  I came out of the hike with about 17 mosquito bites.  He had
only 2 bites.  Other people have reported that when they sleep
outside, some people will have several mosquito bites while other
people will have none.

Generally, I do not wear perfume, deoderant, or have recently washed
hair when I am hiking or biking.  I usually apply sunscreen, but often
use the same brand as other people I am hiking or biking with.  So I
don't think it necessarily has to do with my (or other people) wearing
scented lotion, etc.

What I am looking for is information on what makes some people more
naturally susceptible to moisquito bites than other people. 
Specifically, is there something in our breath, genes, blood, sweat,
etc. that attracks moisquitoes?

Hi bunx!

I despise mosquitos, don't you?  They're the worst part of summer!

Even worse, they'll eat just about anybody.

Or so say the people at SC Johnson, the manufacturers of the bug
repellent, OFF!  They have a "mosquito meter", which provides you with
facts about how tasty you are to a mosquito based on how you answer a
brief series of questions.  Let's start there:

Mosquito Meter
http://www.mosquitoes.com/off_mosquitometer.shtm

Not terribly helpful if you're looking for detailed information, but
if you're willing to play with it a little, it will eventually tell
you that mosquitoes are attracted to heat, moisture and carbon dioxide
- if you breathe and perspire, you're a target, though how tasty a
target varies with height, weight and perspiration levels. 
Apparently, the bigger you are, the better you taste.  I thought this
would be a good jumping off point for researching the question for
you.  (I'm 95% yummy to a mosquito. How about you?)

So what else are mosquitos attracted to, besides heat, moisture and
CO2?  According to several sources, lactic acid, which is produced by
your muscles during exercise, and released from the body through
perspiration:

How Attractive Are You? To Mosquitoes, That Is
http://www.ars.usda.gov/is/AR/archive/feb00/mosq0200.htm

The Ten Most Frequently Asked Questions About Mosquitoes
http://pithaya9.com/mosquito/trivia.html

Additionally, scientists have identified 340 chemical secretions that
attract mosquitoes!

"“So far, we have found more than 340 different chemical scents
produced by human skin, and some of these attract mosquitoes,” says
chemist Ulrich R. Bernier of the ARS’s Mosquito and Fly Research Unit
in Gainesville, Fla. Bernier and his associates presented their
findings in a recent issue of Agricultural Research magazine.

If you think mosquitoes seem to prefer you over others, you are
probably right. It’s most likely because you smell a little different,
no offense intended.

“Mosquitoes use odor to sort attractive people from the unattractive
people to find those that are most tasty,” says entomologist Jerry
Butler of the University of Florida. “They are looking for the highest
rate of human attractants.”"

The Battle for Human Flesh
http://abcnews.go.com/sections/science/DyeHard/dyehard000601.html

So what makes you so tasty?  I've always been taught that women are
bitten more frequently because of their estrogen levels.  Imagine my
surprise when I found this:

"Anhidrotic persons show markedly decreased attractiveness to
mosquitoes (6). Other volatile compounds, derived from sebum, eccrine
and apocrine sweat, or the cutaneous microflora bacterial action on
these secretions, may also act as chemoattractants (6, 20, 21).
Whole-host odors are more attractive than carbon dioxide and lactic
acid alone (22). Floral fragrances from perfumes, soaps, lotions, and
hair-care products may also attract mosquitoes (23). [NOTE: 
Anhidrotic persons are those who sweat very little, if at all. -
missy]

The attractiveness of different persons to the same or different
species of mosquitoes varies substantially (17, 24). In general,
adults are more likely to be bitten than children (17, 25), although
adults may become less attractive to mosquitoes as they age (6). Men
are bitten more readily than women (3, 26). Larger persons tend to
attract more mosquitoes, perhaps because of their greater relative
heat or carbon dioxide output (27)."

Mosquitoes and Mosquito Repellents
http://www.acponline.org/journals/annals/01jun98/mosquito.htm

That's not all that will influence whether or not a mosquito would be
interested in a dinner date with you, though.  Your attractiveness to
mosquitos can also be influenced by the *age* of your sweat, by
surgical procedures, and by medication you're taking!

"Take perspiration. By itself, it appears to be neutral, but as it
ages bacteria begin developing, and that makes perspiration into a
very strong attractant, Butler said."

[...]

"Medications, too, can change an attractive person into one who is
repellent or vice versa. These include heart and blood pressure
medicine and drugs to treat high cholesterol.

McKenzie saw this effect firsthand when a research volunteer was
diagnosed with a brain tumor in the middle of her experiment. Before
his tumor was removed, he was repellent. After surgery, however, he
became very attractive to mosquitoes."

Mosquitoes prove to be selective feeders - The Northwest Florida Daily
News
http://www.nwfdailynews.com/today/newsgard.html

Even more maddening, you might taste bad to a mosquito today, then be
the equivalent of a Ghirardelli Earthquake Sundae (all chocolate ice
cream and extra hot fudge, please) tomorrow!

""People differ in their ability to attract mosquitoes, and each
person's attractiveness can even change from day to day," says Ulrich
Bernier, a chemist at the U.S.D.A.'s Mosquito and Fly Research Unit in
Gainesville, Florida."

Chemists concoct a bait more tantalizing than human flesh
http://www.discover.com/aug_01/featworks.html

So, yes, it is something in our breath, in our blood and in our sweat
that attracts the bloodthirsty little monsters - at least 340
somethings, in varying combinations for all of those!

Oh no!  There's no escaping them, is there?  Alas, probably not.  But
there are things you can do to make yourself less attractive to them:

-use an unscented antiperspirant to keep your sweat down
-wear light clothing.  Mosquitoes are more apt to bite people wearing
dark colors. ( http://www.mosquitoes.com/off_biting.shtm )
-avoid going out during the dawn and dusk periods, when mosquitoes are
most active.
-most importantly, use a repellant that contains the chemical DEET. 
It doesn't taste good to mosquitoes or other biting flies, so they
steer clear.

What is DEET
http://www.mosquitoes.com/off_deet.shtm

I hope this information is useful to you!  Good luck with staying
bite-free this season - if you need any more information, just ask.

missy "starve the mosquitoes, give your blood to people" -ga


Search terms included ["mosquito bites" who], ["mosquito bites"
trivia] and [mosquitoes attract]

This was a really detailed and interesting answer.  The summary was
well written and answered my original question.  I felt I learned a
lot from the summary as to what attracts mosquitos to certain people. 
I liked the additional information that was provided on preventing
bites.  The links were quite good - I especially liked the clinical
link (http://www.acponline.org/journals/annals/01jun98/mosquito.htm). 
My only comment is that I would have liked to have more detailed
scientific/clinical information and links (though I should have
probably specified that in the original question).

You may be interested in a current study published in the New England
Journal of Medicine comparing the effectiveness of different mosquito
repellents:

http://content.nejm.org/cgi/content/short/347/1/13?query=TOC