Bug Bite Genetics

mosquitoImage2Editor’s note: Pending an FDA decision, 23andMe no longer offers new customers access to health reports referred to in this post. Customers who received their health information prior to November 22, 2013 will still be able to see their health reports, but those who purchased after that time will only have access to ancestry information as well as access to their uninterpreted raw data. These new customers may receive health reports in the future dependent on FDA marketing authorization.

Some of us get mosquito bites that look more like marble-sized welts while others get bites that barely leave a mark.

It turns out that our genetics plays a role in those different reactions, according to recent data compiled by 23andMe researchers.

When a mosquito bites — it’s only the female that sips our blood — it leaves behind saliva that triggers an immune response in people. For some the bite triggers an immediate reaction, for others it takes a few days, but the results are often the same kind of itching, swelling and redness.

23andMe researchers found an association between an individual’s genetics and the severity of the reaction to the bite.

In people with European ancestry, those with the CC genotype at rs309375 were more likely to report smaller mosquito bites than those with the AC genotype. On the other hand, those who are AA at rs309375 were more likely to report larger bites.

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There are a lot of reasons to study our response to mosquito bites. For one, mosquitoes transmit diseases, such as Dengue fever, West Nile Virus and malaria. (Malaria is spread by anopheles mosquito, which have largely been eradicated from the United States.) So knowing how people respond to bites as well as why some people may be more susceptible to getting bit, could help in efforts to stop the spread of the disease.

But just as 23andMe’s researchers have done in looking at other traits, the different ways people respond to getting bit also gives researchers a better understanding of the genetic differences among people. It can also give us more insight into the biological processes involved in of traits and conditions.


  • JohnF

    CC genotype at … where? Something is missing from this post!

    • ScottH

      John, My apologies. The SNP is rs309375 and the post and widget now should be in order.

  • UmeshS

    Will having AA/AC/CC genotype affect whether we get the diseases due to mosquito bite or does it only tell us whether we’ll get a bigger or smaller bite mark? Also does the inflammation due to mosquito bite help in killing the organisms spread by the bite?

    • ScottH

      The association is just focused on the size of the bite.

  • JimC

    I’m AA and of mostly (99%+) Han Chinese extraction. I wonder how this association fares with folks of non-European ethnicities. In my case, I have a relatively severe reaction: roughly 2″ diameter welts in response to mosquito bites, sometimes with significant edema in the affected limb well beyond the bite lasting for several days afterwards.

    I’m glad to see that 23andMe is continuing to mine new GWAS results from the customer data set. It’s awesome that as customers, we can all contribute to the discovery of novel findings that may eventually prove to be clinically actionable.

    • ScottH

      At the moment the results we have are focused on people with European ancestry.

  • Genny

    Hmmm…I am 99% European with AC. My reaction is VERY severe. I’m talking, like, it looks like I have a tennis ball under my skin. a few weeks ago I got a bite on my ankle and I saw the mosquito so I know it was that)- and the whole inside of my foot, half way down the bottom, and a good few inches up past my ankle, blew up. I couldn’t walk right for several days. And that is not really a unique experience for me. They always blow up big.

    I know it says, “More likely” which means not everyone will have the reaction as described (in this case, average). I wonder why I react so severely if I’m an AC? No big deal, just curious.

    • Jason T

      You better start buying some “Off” by the gallon !

  • Carol Schaffer

    How weird, my genotype is CC, I am 99.9% European, and yet I get massive mosquito bites that I excoriate to the point of scars that take a month to heal… Anyone else with conflicting results that don’t match your phenotype?

  • Jessica

    I am wondering if people who seem to get bitten MORE, i.e. attract more mosquitos, are just those who notice them more because of their more severe reactions to bites, or if something about them actually attracts more mosquitos and they do therefore get bitten more. Anyone look at that?

  • Jan

    I am AC. Always bitten, even when others don’t even notice the mosquities, and the bites last for days to a week. My bites vary significantly by geographic location when bitten. I get raised, angry, red, teacup size bites from mosquitoes in the California Sierra foothills, but bites 1/8 that size from mosquitoes at higher elevations (Lake Tahoe). My sister is rarely bitten.

  • Judy

    I am 99.8% European, AA, and hardly ever get bitten, while others all around me do. When I do suffer a bite, it really doesn’t bother me. My son, whom I haven’t had tested, gets huge, itchy bites. I think the reason I don’t is because I take a combination of B vitamins (Homocysteine Modulators) which consists of Vitamin B6, Vitamin B12 and Folic Acid, Supposedly an “old wives tale”, but for me, it seems to work. The genes seem to be trumped in my case!

  • Bell

    Our youngest son would have a boil immediately . This would progress to a carbuncle within 48 hours. He developed Chrones disease at age 20 and died at age 28 from an infection around the heart.

  • Laura

    I am CC and it explains a lot. I have never in my life had an itchy mosquito bite. They rarely bite, but when I do notice it happen, my skin never has any reaction. I have always joked about this as my one secret superpower.

  • Sander W. van der Laan

    So, where’s the scientific publication? Or am I missing a link somewhere? :-)

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