Why do mosquitos bite people?
Hey. I'm Melissa.
Jam:I'm Jam.
Melissa:And I'm a chemist.
Jam:And I'm not.
Melissa:And welcome to Chemistry For Your Life.
Jam:The podcast helps you understand the chemistry of your everyday life.
Melissa:Jam, it's so nice to see you again in person after so long.
Jam:In person, meaning in video, but yes.
Melissa:Yes. I'm sorry. I meant in real time rather than text only communication.
Jam:Totally. We're seeing each other and hearing each other. And it is live, and that's as good as it you can you can kinda get right now anyway.
Melissa:Except for our impromptu Target meetup, which was very Exciting.
Jam:That's true. That's true. You can't, I mean, you can't plan that kind of stuff. That's just
Melissa:No.
Jam:That was very serendipitous.
Melissa:It was. I was so happy. My face was so red in that picture because I was just full of joy, and that's what happens when I'm happy is I get flushed. And so
Jam:One thing that was kinda funny too is I had enough time that I saw you. You kinda went past me at first. Had enough time to take a photo, which is kinda creepy, but take a photo, Send it to our, like, friend group text that we were already chatting with with different people in before you noticed me,
Melissa:Which Yeah. You creeped.
Jam:Which is always fun. We used to call that sniping, where you can if you can take a photo of somebody and send it to them before they see you. But
Melissa:You sniped me.
Jam:Yep. Sniped you.
Melissa:Well, are you ready to learn some chemistry? We've been on a little bit of a break here.
Jam:Yes. I'm very ready. I haven't had a chemistry lesson in probably 3 weeks, would you guess?
Melissa:I think, yeah, it's been about 3 weeks. I kinda forgot that we even had a podcast.
Jam:Yeah. We kinda got ahead, which was great. But, yeah, It's weird to then not have, like, the weekly chemistry time in my life, so I'm I'm ready for it.
Melissa:Okay. Well, this week is going to be the beginning of a series.
Jam:Nice. I like when we do series.
Melissa:Me too. And our listeners, we took a poll One longer episode or shorter episodes, and they said multiple shorter episodes is better.
Jam:So Nice.
Melissa:We heard you guys. So this is gonna be 2 or 3 parts depending on how the rest of the topic shake out, but Okay. Our topic is berry berry Summary.
Jam:Okay. Nice.
Melissa:It's a series on mosquitoes.
Jam:Oh, nice. So
Melissa:why do mosquitoes bite people? Why do mosquitoes bite some people more than others? Why do mosquitoes bites itch? Why does insect repellent work? What's the best insect repellent?
Melissa:We're gonna dig in to all these questions, and I've been getting a lot of them from a lot of listeners over the past few weeks. So
Jam:Nice. That's those are great questions. And mosquitoes are certainly a very, very infamous part of summer. So We're right in the heat of that for sure.
Melissa:And I've been noticing other people getting bit a lot and me being around them and that not happening to me. So my curiosity was peaked, and then a bunch of people contacted us.
Jam:Mhmm.
Melissa:So if you're one of the people that contacted us, I can't search our Instagram messages for mosquito the same way you can in your other messages. So I couldn't find all of those. So if you're one of those people and I'm not giving you credit, Just message us, and I will put you on there.
Jam:Nice.
Melissa:But I think some of the people who asked was Vianette g, Mason k, Nicole b. There have been lots of people who have asked questions about this.
Jam:Nice. That's usually a good sign too. There's a few times where we've had, like, like, somehow, all at once, a few people ask about the
Melissa:Right.
Jam:This is some chemistry that is in their life that they wanna know about.
Melissa:Oh, a 100%. And I think I haven't researched everything, but I think why the bites itch and the how the repellent works is more chemistry related. Today's topic is heavily biology. Okay. So there is obviously chemical aspects because Everything is chemicals.
Melissa:So carbon dioxide, our smell, all of those things are chemicals.
Jam:Mhmm.
Melissa:But it's also biology topic. So As always, if there is a biologist or another scientist who studies this that's listening right now, please please please feel free to email us, Touch base with us. Let us know so that we can update this information. But a lot of it is also new. I found a lot of information from papers from 2014 and 2019.
Jam:Interesting. I think
Melissa:I think we're still learning.
Jam:Yeah.
Melissa:Okay. We're gonna dig in. Okay. Good. We're going.
Melissa:Okay.
Jam:I'm ready.
Melissa:The first question is, why do mosquitoes bite people at all?
Jam:The amen. That's a great place to start.
Melissa:Well, here's the thing.
Jam:Because if they didn't, none of the other questions would be necessary. So Mhmm.
Melissa:Yeah. And this made me soften up towards mosquitoes a little bit. They're trying to Get blood so they have a protein source for their eggs. They to produce eggs. So they're just trying to get their babies born.
Melissa:Do you know?
Jam:Yeah. Hey. We try to do the same thing, don't we?
Melissa:I know. We're just trying to get get some life going for your kids. That's all you're trying to do.
Jam:Yeah. Interesting.
Melissa:So I was like, okay. I guess that's an acceptable reason to bite people. But then when you think about the fact that that means there's gonna be more mosquitoes, Then you don't want that anymore, but I kinda get the instinctual drive. You know?
Jam:Right. Right. Right.
Melissa:So because of that, only female mosquitoes Bite humans.
Jam:Wow. Dude, that's crazy. I did not know that.
Melissa:Neither did I. I thought it was one of those fake Facts that people share, you know?
Jam:Yeah. Big facts.
Melissa:But it's real.
Jam:Big facts. That sounds like a little bit of an oxymoron.
Melissa:People will be like, interesting fact, and then it's something that's not true. Yeah. So so that's why they Bite people. But then the next big question on scientists' minds is how do they find humans to bite?
Jam:Mhmm.
Melissa:So what have you heard?
Jam:Okay. Well, I'm kind of in the same boat as you. I don't get bit A ton by mosquitoes, like, a lot of times but I do get bit some, but people will be like, man, I'm getting eaten up right now. And I'm like, I've seen I've seen a couple, Maybe.
Melissa:Yeah. Me too.
Jam:Usually, it's others around me. And so I've certainly heard things about blood type. In fact, I was just Hearing people talk about that the other day, about supposing that some blood types are more Appealing to mosquitoes and others, no idea if that's true. But that might be the only I mean, maybe there's some sort of, Yeah. Something I think of that might make a difference I mean, I guess they could maybe smell us, but I I feel like I can't think of any reason why they prefer 1 person over another unless it had to do with our something about our blood that benefited them.
Melissa:Okay. Wow. I have heard that too, blood types.
Jam:Mhmm.
Melissa:I've heard also that it has to do with c o two that you express in your skin.
Jam:Oh.
Melissa:And I've heard that it's because your blood is sweet. You know? Moms always say that to their babies. They're like, it's because your blood's so sweet. Uh-huh.
Melissa:It's because you're so sweet. But that's not it. Sorry, moms. It does have to do with Sweat.
Jam:Okay.
Melissa:Carbon dioxide is involved. Mhmm. And that's pretty much it.
Jam:Nice. So not blood type?
Melissa:Not blood at all.
Jam:That's awesome. Great.
Melissa:Mosquitoes use carbon dioxide, body odor, and heat to detect their prey.
Jam:Okay.
Melissa:So you're right about them smelling us.
Jam:Okay.
Melissa:They can smell us, But the warmth of our bodies and the carbon dioxide are important.
Jam:Okay. Got it. So if we were, like, super cold, they might pass us over?
Melissa:Maybe so.
Jam:Interesting.
Melissa:There was one study where they put out blood with human odors in carbon dioxide and Kept the blood at room temperature instead of being warm, and the mosquitoes did not eat it.
Jam:Woah. Mhmm. Interesting. Yeah. That's so weird.
Jam:So I know. So they can, like, sense our heat in some way. Maybe that's too much of a biology biological question. Can I see it? Or
Melissa:Well, let me get into it here. Alright. I jumped ahead a little because you asked the question, so I was excited to answer. But K. The carbon dioxide seems to play a role in that heat sensing.
Jam:Okay.
Melissa:So I used to think also that carbon dioxide Came out through your skin. Every single article I read said it was just the carbon dioxide that we breathe out. Oh. So the carbon dioxide that we breathe out has an effect on mosquitoes. K.
Melissa:And one study, They sort of figured that out and knew that that was probably it. So one study basically just Inhibited their carbon dioxide in receptors. The same way we talked about the carbon dioxide receptors on our tongue, how they inhibited those. Yeah. They did that to mosquitoes.
Melissa:I think they genetically mutated them. So they actually did work on changing the DNA of the mosquitoes, which is crazy.
Jam:Yeah. That's crazy.
Melissa:And they inhibited their ability to sense carbon dioxide. This is in one study in 2014.
Jam:Mhmm.
Melissa:And when they did that, In the presence of CO 2, the mosquitoes who still had their carbon dioxide sensor had more movement than mosquitoes without it. So something about their ability to sense carbon dioxide gave them a better ability to move. And they had the ones without the carbon dioxide sensing had less attraction to human body temperature in the presence of CO 2. So it's almost like that study says, in the presence of CO two detection, They can move more, and they can sense body temperature more.
Jam:That's kinda the most primary important ingredient. And the other things are kind of dependent on
Melissa:it. Yes. Now I should say, in that study, when they actually stuck a human arm into a place with the mosquitoes, The ones with and without the CO two still were able to find the human and feed on it. Mhmm. So there's more than just CO two.
Melissa:It seems like From that study, there's more than just the carbon dioxide and the body temperature. So then you get into deeper studies and try to kinda figure out what else it is. Yeah. And that's where this 2019 study came in.
Jam:Okay.
Melissa:This 2019 study, they dug into the human odors. Mhmm. They found a receptor on the antenna that seemed to play an important role.
Jam:Okay.
Melissa:And they disabled it. And this receptor detected for volatile acids on our skin and in our sweat such as lactic acid
Jam:Mhmm.
Melissa:Or they're known as carboxylic acid. It's a special functional group. We've talked about functional groups.
Jam:Mhmm.
Melissa:So it's just a collection of atoms. So it's a sort of a classification of a certain type of acid. And when scientists disrupted that ability to sense lactic acid, those mosquitoes had a reduced attraction to human host.
Jam:Woah.
Melissa:And the presence or absence of CO 2 also played a role in that. Mhmm. So it seems like from all these studies I read, there's so many studies about this Mhmm. That the chemicals in our sweat, Plus the chemicals that we exhale and our body temperature all contribute. They all have to coincide together for the mosquitoes to be able to find us.
Jam:Wow.
Melissa:Mhmm.
Jam:They it sounds like But if you if you knew all that ahead time, it seems like there's a lot of reasons there's a lot of factors that have to be right for them to find us. So So it almost makes it seem like it's harder. Like, it'd be hard for them to find us. But then in real life, when you're outside in summer in places like Texas where we live, It seems like they're everywhere, but you just wouldn't think about it being that complicated.
Melissa:Yeah. You really would not think about it being that complicated. And It's interesting because they would isolate something and it would show an effect, you know, in the presence or absence of c o two, for example. There was that effect in simplistic studies where they wouldn't be attracted to blood or human body temperature without CO 2 or whatever. But then you put a real human in, and there's so much more going on that there's still even without their ability to detect CO 2, they're still coming at the human.
Jam:Right.
Melissa:And then those scientists theorized, maybe c o two is, like, the 1st detection symbol. The 1st detection element, I guess, I should say.
Jam:Mhmm.
Melissa:And that indicates to them that there's prey nearby, and then they can hone in. So when you're already very close to the mosquito, all your Other things, your odors, the lactic acid, the volatile acid in your skin, your body temperature, that's more important. That's overwhelming to the Mickey
Jam:to get those
Melissa:senses, and you don't need the CO 2 detection anymore. Mhmm.
Jam:Got it. Okay. Got it. That makes sense. Because, like, any Mammal pretty much would be exhaling CO 2, and so it'd be a really good first detection kinda thing.
Jam:It's like, is something around that I could go get some blood from something that's in that broad category that I might that might work for me.
Melissa:There was some Studies, it seemed, or some of what they were looking into was how they're so attracted to humans. Mhmm.
Jam:So
Melissa:there was some studies on that, but I'm a little foggy on the details because that was Heavy into biology papers that were just barely in my ability to grasp. So And this really matters because mosquitoes can carry diseases with them that can kill a lot of people. So this may seem To some people, like, they're doing this research just to find out about this a nuisance kind of that bothers us, But, actually, these are life saving things to learn about because if you learn how mosquitoes can detect humans and come towards them, then you can use that to develop other chemicals or other things that can repel them or that can keep them from Being able to impact humans, and then you're really saving lives from keeping them from transmitting diseases. There was a number. I should find it in the future, but for one of the next episodes, but they gave a number in one of these papers that said how many people can die of diseases transmitted by mosquitoes every year, and it was crazy.
Jam:Oh, wow. Yikes.
Melissa:So, yes, there's definitely this research is important because of that, that we're doing more than just keeping the annoying bugs off of us. We're these researchers are trying to save lives Yeah. By doing this stuff.
Jam:So That makes sense. I wouldn't have thought about that primarily. I would have thought about it. Secondly, like, they're annoying, and They are, like, just frustrating, and we for the most part, as humans, Anything that kinda bugs us that we can figure out a way to prevent, we just kinda do about nature. Oh, yeah.
Jam:Bugs us. Yeah. So that's what I would've thought of. But, yeah, you're right. Like, the the disease part is probably huge.
Jam:I didn't I didn't know that. I'd definitely be interested to hear that that statistic.
Melissa:Yeah. I'll be sure to bring that into the next episode. But, also, they talked about, now that we know this in the lactic acid paper, they mentioned, now that We know this. We can utilize this information to develop better methods of keeping mosquitoes away from humans, Including putting lactic acid, mosquito traps, or, you know, they mentioned a few things that you're just like, oh, Yeah. I guess that is what the more knowledge we have, the more we can protect ourselves against this Mosquito.
Jam:Yeah. Ding.
Melissa:So that's it. There's 3 factors that we can easily identify and talk about. I'm sure it's a much more complicated issue than this, but these are the 3 main things that scientists seem to have reported on at this time. I'm sure we'll learn a lot more.
Jam:Okay. So, it's Primarily carbon dioxide. Right? So mosquitoes are flying around, And the thing they seem to be looking for first is some carbon dioxide, which gives them a sense that some Pray is nearby that might be worth further investigation.
Melissa:Right.
Jam:And then The next one was body heat. Right?
Melissa:I don't know. Order
Jam:after that.
Melissa:There wasn't really an order. Okay. It did seem That the carbon dioxide was the 1st detection Mhmm. Almost the first signal that something was happening. But after that, It seemed the other ones were just all sort of together.
Jam:Okay. So body heat and then odors from our bodies like, Lactic acid and and potentially other things that contribute to an odor that they something that they can Detect from us
Melissa:Right.
Jam:Would help them hone in on us specifically.
Melissa:Yep. So
Jam:that could could that I mean, we'll get into this later or whatever, but Could that make the difference then? Like okay. Obviously, all of us are breathing out CO 2. But when it comes down to the mosquito choosing between you or me, Body heat and lactic acid or whatever else, do they make distinctions based on that, or do people Or do we know or what?
Melissa:That is a question for next week.
Jam:Oh, okay.
Melissa:So I'm gonna leave that on a cliffhanger because That the reason why people 1 person over another is chosen is gonna be Another episode.
Jam:Okay. Sweet. I like it. Little cliffhanger there.
Melissa:A little cliffhanger. So we're gonna talk In the next few episodes, we're gonna talk about why some people are chosen over others. We're gonna talk about why they itch at all, And we're gonna talk about how to repel them.
Jam:Nice. Okay. Sweet. I like it.
Melissa:But I figured short bites would be easier than big bites, especially because this first topic is so biology heavy. Mhmm. Although the lactic acids, the functional groups in the acids that are volatile, That's chemical based. And the carbon dioxide that we breathe out, that's a chemical sensor.
Jam:Mhmm.
Melissa:So they're the mosquitoes have chemical sensors
Jam:Right.
Melissa:That are indicating that humans are present. But the identification of the sensors and doing Genetic engineering to remove those sensors Uh-huh. That is very biology.
Jam:Nice. Also like what you did there, and he said some small bites and some big bites.
Melissa:That was an accident. I just, like, set you up to take those Swings. You know?
Jam:Yeah. I wish there was an easier pun with the word mosquito. I'll try to think and incorporate 1 over the next few weeks. Bite Bite seems like it it's a little bit on the nose. It's still still funny, but I let's see if I can find a different one that you don't see coming.
Melissa:Well, good job. That was it.
Jam:Sweet. I like it. I'm interested in this series for sure, and, I just yeah. There's a lot of questions about it. I'm glad we're taking it 1 at a time.
Jam:Seems like they all are worth their their own, section, so to speak.
Melissa:The only thing I wanna add is to remind you that the CO two detection also seems to impact their movement. So they
Jam:Oh, right.
Melissa:The ability to sense CO 2 seems to hone their movement and detection of human body temperature.
Jam:Got it.
Melissa:It seemed as I was reading, it almost seemed like CO 2 was sort of a gateway that opened these other pathways. So CO 2 plays a role in the detection of the lactic acids and your ability to move and get body temperature. It's not everything Mhmm. But it does enhance those or play a role or do something to make the mosquitoes be better. But, really, The ability to do all of those things at once seems to be the best option.
Jam:Mhmm. Got it. Okay. Got it.
Melissa:Well, that's all I have for you. Do you want to Share the number one most exciting thing that's happened to you in the past few weeks.
Jam:Totally. Yeah. So we've talked born. So
Melissa:Yay. We
Jam:had our baby about 3 weeks ago, and we had just enough heads up They were kinda able to get ahead on podcast stuff, just enough to not be not miss a week.
Melissa:It was very close at the end.
Jam:Yeah. He came a little early, but all was well. Everything went well. Still adjusting to To life with a kid. I mean, anyone who has a kid knows what that's about and knows way more than I do about how long it might take me to adjust.
Jam:But
Melissa:Right.
Jam:Yeah. Just adapting and and, getting used to taking care of a little one that can't do anything for himself. So, but, yeah, it's great. I'm loving it.
Melissa:I think my happy thing is that I got to meet him through a window.
Jam:Yes.
Melissa:I was so so so so so happy, And I got a video sent to me where Emily was talking about chemistry for your life, and he was Smiling. Yeah. She said intermolecular forces, and he smiled. And she said, do you love it? And he This looks so happy.
Melissa:I've watched that video so many times. Yeah.
Jam:We try to do whatever we can to see if we can get him to smile, and Like, tone of voice is a big part of it. Then also sometimes it seems like something that enters his own head, whatever. I'm not sure what baby thoughts are like. Was it making him smile out of nowhere?
Melissa:No. It was because of chemistry for real life. It was because of intermolecular forces.
Jam:Yeah. Definitely.
Melissa:Definitely.
Jam:For sure was that.
Melissa:Well, I really loved all those videos, and I know that he smiles because of intermolecular forces, but some parents are being pretty careful about putting their kids' images on The Internet. So what are you guys thinking? Do you wanna be able to put a picture up? Or
Jam:We're not totally sure yet. We haven't really thought through that a lot, honestly, but we're gonna try to figure that out. So if you guys end up seeing a photo, then you'll know what we figured out. And if not, it might it might be that we just do that a little bit later, or we Space it out so that he is not, like, you know, all over the Internet, his whole childhood kinda thing. Right.
Jam:Just hard to know. Like, I wish I had a good resource to to follow on that. But I'm just we're trying to be careful until we kinda decide what seems right. So yeah.
Melissa:Right. It's hard because there's a whole generation of kids whose whole life was on Facebook Mhmm. And Instagram and stuff.
Jam:Yeah.
Melissa:They haven't really become adults yet, so don't really know.
Jam:Right. And, like, I got to decide what was posted about me, but only as far back as, like, high school when Facebook Right. Happened or whatever. So There's a whole my whole earlier than that childhood was just private, you know, for our family or whatever. So it's just kinda interesting to to think through.
Jam:So we'll see, but, Hopefully, we can figure that out. If and if any listeners have any good thoughts or resources or books or something like that on that topic, I'd certainly love any recommendations. So,
Melissa:Yeah. Definitely.
Jam:Send those our way.
Melissa:Well, congratulations on being a daddy jam.
Jam:Thank you. Yeah. Thanks. I'm I'm loving it.
Melissa:So fun.
Jam:It's awesome. It's as so far as awesome as people say. So
Melissa:Yay. Well, I wish I could be there and hold him and snuggle with him, but due to coronavirus and us all Trying to keep safe. I will continue to stare at him through windows whenever I have
Jam:the chance. Perfect. Perfect.
Melissa:Alright. Well, thanks so much for taking time out of your dad's Schedule away from your precious baby to hang out with us and to learn about mosquitoes. And thanks to all you listeners for Coming and learning about mosquitoes as well.
Jam:Well, thanks so much for teaching us and for starting this cool series. I'm excited about these future episodes, And I'm glad that we're back to recording and having some chemistry in my life on a weekly basis. So Mohsin, I have a lot of ideas for Topics of chemistry in everyday life, but wanna hear from you just like mosquitoes, which we heard from a lot of you guys. So if you have questions or ideas, you can reach out to us on Gmail, Twitter, Instagram, Facebook at chem for your life. That's contribute to cover the cost of making it, go to kodashfi.com/chem for your life and donate the cost of a cup of coffee.
Jam:If you aren't able to donate, you can still help us by subscribing on your favorite podcast app and rating and writing a review on Apple Podcasts. That helps us to build a share chemistry with even more people.
Melissa:This episode of chemistry free life was created by Melissa Collini and J. M. Robinson. References for this episode can be found in our show notes or on our website. Jam Robinson is our producer, and we'd like to give a special thanks to s Flint and v Garza who reviewed this episode.
