Meet the mites that live on you: from demodex to dust mites and scabies

0:28It looks like it's got tiny little eyes. cardinal symptoms of scabies. I've never seen a case of scabies where someone hasn't been harangued by itching.

0:41Hello and welcome to Strange Health from The Conversation, the show where we explore all the weird and wonderful stuff that your body gets up to. I'm Katie Edwards, I'm health and medicine editor at The Conversation in the UK, and we're an independent source of news and analysis powered by academics and journalists working together to make evidence accessible. And I'm joined by co-host Dan. Hi guys again, I'm Dan Bangor. I'm a GP in Lecturer in Health and Life Sciences at the University of Bristol. Today we're talking about something that will make a lot of people itch just by hearing about it.

1:15So I apologise in advance because I've been doing it as well. We're talking about mites. They're the tiny creatures that live on your skin, in your paws, in your bedding and sometimes they're in places you'd really rather not think about. And if your brain went to fumigation or burn the house down you are not alone but please don't do it don't do it this episode is going to tell you a little bit more about these little creepy crawlies that live on your skin and why you shouldn't see it. Yeah so this this episode has actually been inspired by these videos that I've been watching on social media where people have been um mainly women i have to say who've been doing the faces and putting makeup on and then they'll be like oh i'm mid makeup and my face is itching or like they've done a full face of makeup and then face is itching and they're scratching the nose and stuff and um it seems like uh that's mites attacking the face or the eyelashes and here's one of these videos that i found have a look down you ever got done doing your makeup and your face started getting okay so this This is a woman.

2:20She's talking about face mites. Don't have to treat them. She's traumatised. She's going to use hypochloric spray on her face. She's going to kill them. So she's saying, this woman here, she's saying that your face starts getting tingly so you can actually feel the mites. What we're talking about here is demodex, those little mites that live in and around our face, particularly in our eyelashes. and that sort of itchiness that you can sometimes feel around your face, probably not related to them in all honesty. It's more likely to be related to other dry skin conditions or other skin conditions which affect the face.

2:57So can you kill them with hypochlorous spray then? Because that's a spray that became popular during COVID, didn't it? Where people were spraying it. Yeah, and I think they reside within these little pores and sometimes they can live quite deep down. So I wouldn't say that it's an instant answer, I have to say. and I think more than anything else we just need to accept that these mites are a usual part of our body and that we can't really necessarily do anything about them well let me just reassure everyone by showing this picture because who wouldn't want one of these little beauties living on your fizzog look at that oh there's something a bit extraterrestrial about it in a nice sort of way it's um how to say it's it's a worm and it looks well it looks like a worm oh no i'll tell you what it looks like you know when kids are really young and they start first playing with play-doh like plasticine it's like that isn't it the roll it and then just make like a little head thing at the the top it's got eight legs right up at the front and it looks like it's got it looks like it's got tiny little eyes looks a little bit like the alien queen as well doesn't know the sort of like sack that she's got on the end from where all the alien eggs come from oh damn that's the rim miniature little alien queens honestly i'm trying my best to be all right about this but that is not helping a bag of a sack of eggs and actually what they what they're doing there is feeding off the oil within the paws as well so the little oil gobblers how cute damn oil gobblers with oil gobblers right i think you need to stop yeah i think that's the thing we again we've all got loads of bacteria fungi and yes mites living with us all the time literally trillions we've got a microbiome a microorganism residing upon our bodies inside and out all the time i know we're supposed to i'm supposed to feel cool about this like yeah great we're a walking ecosystem but it's not just a nice phrase is it that is what we are no it's not it's not branding it's biology your skin is a habitat it's got lots of different functions.

4:59But essentially, it's an immune barrier stopping things from outside the body affecting the inside for the worse. And even then, if you feel yourself itching, the story is rarely that it's mites that are there and attacking you. It's usually something else has changed and the ecosystem has shifted. And that itch is really contagious too, isn't it? Just the talk of itching or lice or mites or the pictures that we've just seen, the sight of someone scratching as well can really set us off yeah you've set me off i'm desperate to itch me yeah i know i know and i've it's just the talking about it is contagious because our brains are masters of mimicry when we start thinking about itching we activate the same neural pathways as when we actually itch and we're also very receptive as well to the actions of others we would copy each other yawning if we were tired and we also notice people scratching we notice them sort of attending to that itch that's on their hand, on their arm, in their hair, driven by the idea that we might have picked something up that they have as well.

6:00Go on, pack it in! I know, sorry. I'm sorry to viewers at home, Laurie also set off as well. Genuinely, I think they are attacking me though. I am feeling it. They can't, it's all in your head, it's all in your head. Yeah, it's what's played for me to be though, isn't it that? So today we're asking, which of these microscopic housemates are normal? Which ones can cause real problems like scabies? which has actually had a bit of an outbreak, hasn't it, in the UK at the moment. And why do we find the idea of them so upsetting? To find out more about what these mites are actually doing on his body, I spoke to a biologist who, I must admit, I did love a bit.

6:39She's very cool. Who's an actual expert in mites and men. Dan, did you see what I did? A little bit of a literary joke. A little bit of a John Steinbeck pun. Yeah, yeah. It's lovely. just to show that I'm really quite pretentious. So Alejandra Perotti researchers the relationship between mites and humans. So I asked her to tell me about some of them for our Ask the Expert section.

7:08Alejandra Perotti, hello, thank you for being with us today. So you're a professor of invertebrate biology at the University of Reading in the UK, and you're an expert on all things little mites that live on and around our bodies. Welcome to Strange Health. I'm very happy to be here. So when I hear mites on skin, it sounds like it's time to get fumigated. It makes me feel very nervous. Can you start by telling us how normal this actually is? I think the problem is that we are no longer familiar with seeing bugs or seeing invertebrates or insects around us, especially in the environment we live in.

7:53It's very rare to see even a fly inside the house. Everything similar and on top of our skin or living from our skin possibly scares the hell out of a lot of people. So all mammals have follicular mites that live inside the pores of the skin. Most people don't know that they have these mites in their skin and possibly they are completely unaware. They have a very healthy skin and they have a lot of mites, but they don't produce any problems. Okay, so let's focus in on demodex. Demodex mites live on almost all human skin. At what point in life do we get them and how did they arrive there in the first place?

8:37We inherited them from our mothers. So when we are born, the mites are transferred. It has been studied not in humans, in cows and in rats, for example, how the transference happened. Babies have very few mites. The population in each human grows to big numbers after we reach puberty. And then after 40, 50 years old, the person develops bigger pores and then they have more room to live. So the population expands. And the prevalence in elders is 100%. So all elders, for example, over 60 have follicular mites. The ones that live in our skin are the follicular mites. Humans, we carry two species.

9:24One is a very tiny, short one called the Modex brevis. The other is longer, but they are minute. Both are around 200 micrometers in length. So they are the Modex folliculorum and it's the species we mainly studied. We did a full biology study of this species. and we live completely in harmony with these mites, both species. They are symbionts of our skin. For example, we give them shelter because they live inside our pores. At the same time, they clean our pores. And you wouldn't be able to feel them, even if you had loads of mites, you wouldn't be able to feel them. No, no, no, no, no. They are active in the night.

10:08So in the evening, we secrete a hormone called melatonin and then it puts us to sleep. we start getting sleepy. And it's when we secret this melatonin. However, we discovered that these mites do not secret melatonin. They lost the sheens to produce melatonin because they have a reduced genome because of the symbiotic living lifestyle. And so they lost sheens to produce melatonin and they consume our own melatonin because they live in the pores. The melatonin is secreted in the skin. So perfect for them. In arthropods, in these small animals, melatonin actually triggers activity like reproduction, mating.

10:58So when we go to sleep, when we are sleeping, the mites are walking all over our face. Mainly females visit other pores to reproduce, to mate. And the whole thing gets very active because we have done experiments collecting with the special tapes that you put on your skin, collecting the mites from our skin or the skin of the participants of the experiments, and they become very active while we are sleeping. So the people have to sleep with this tape. In the morning, you can see that the mites during the night got trapped in the tape because they were visiting other pores. The females are very mobile in the night.

11:41And my hypothesis is because they have very interesting features. For example, the males have the penis in the back. It's like you have the penis here. So if this is here, yeah, and then you have the mite. Let me see if I can find the small one. So you have the mite attached here. So the mite is attached. So with the legs here holding the hair inside the pore, this is the penis coming upwards. Yes? Oh, okay. The female enters in the pore and sticks the penis in the vagina. So she's hugging the male and the male is hugging the hair. And it's how they made it. Gosh, and that's all happening in our paws at night?

12:35And all happening while you are sleeping. Sweet dreams. Do you know, I was going to say before you went into that story, I was going to say that you'd managed to make these mites sound quite adorable. And then we got the hugging. Yes, and then I have seen big populations, big families actually inside ports of elders. For example, people over 65, 70, 80, and you can have up to 18 mites inside the pore because age, our pores enlarge, especially on the nose. And then they have more room and you have the whole family there. You have the adults, you have young ones that are nymphs, larvae, eggs inside the pore, the same pore, up to 18 mites.

13:28And this is a good thing. The volunteers that allow us to sample didn't have any skin problems. Oh gosh, yeah, that's the opposite of what I thought. I thought if you had too many of them, they cause kind of rashes and red patches. I have thousands of them in my face and I don't have any skin problems. When I need to look at them, I just put a tape and I get mites and I get handwritten. The only issues show up when the host, so the person that carries the mites, is immunocompromised. And then they can have some skin conditions, and these skin conditions gather more mites, or the mites go out of control and reproduce out of control in certain parts of the skin.

14:18So would that be things like rosacea? Possibly, yes. But it's not because it's not the mites. If a person has a condition on the skin, for example, has an infection of a bacterium, the modeks will go there and will eat on this bacterium. So they will congregate there and they will reproduce probably associated to this patch of the skin. And then you have a big population of mites, but you cannot see the mites. You cannot recognize that you have mites. You only can observe and study them under the microscope. Oh, you're like a mite defender. Well, I'm sure you have plenty of mites and you don't have any problem living with the mites and the mites living with you.

15:06So how they can explain that all humans carry the mites and don't have any, most people don't have any skin conditions, skin disease. Wow. Wow. That's astonishing. I've been reading online about some people who think that they've got an infestation of demodex and they are giving each other tips on how to kill the demodex and saying, you know, you should use tea tree oil and you should wash your pillows and your bed clothes on really hot temperatures and dry them on really hot temperatures to try and kill these things. And some people have mentioned that they feel like their lives have been ruined by these demodex mites and that they actually feel pain and they feel them crawling on the face.

16:03I'm talking from a scientific point of view. We did scientific studies. What you read on the internet sometimes are people that don't have any scientific training. We work also on a topic called delusional parasitosis. It's very widespread. And I think it's spreading even more now. I get contacted roughly once a week by somebody that sends me an email and tells me that if I can look at the photographs they took with the phone of the mites on their skin and that they collected a lot of mites in an envelope. They all have the same pattern of behavior. and when you look at the photos they send you, they just send you photos of the skin that you cannot see anything, of course, because the mites are 200 micrometers in length.

16:51But they are obsessed that something is crawling on their skin. So can you tell me then, what about dust mites that live in our clothing and bedding? What do we know about them and, you know, the life cycle? They originated in nests, normally bird nests, but they ended up? living with us in our houses. It's a very good environment for them. So there are some species that actually the typical houses might be tiny as well, around 400 micrometers, a little bit bigger than the MODX. They are associated in general with the bed linen, with the mattresses, but they can be found in the bedrooms, in carpets as well.

17:36As long as there is sufficient humidity, over 60 65 % humidity they are found inside a room. For example, I did an experiment some years ago. You have to do it when you leave the bed. The moment you leave the bed, because the humidity of your body is still on the surface of the bed linen. So I tape the whole bed linen, especially the part I was laying on. And then I remove the tape, like I waited 10 minutes, because then they go down to the mattress. So you have to capture them when they are still on the surface because when you are sleeping, you sweat, and there is humidity, and it's warm. It's a perfect environment.

18:21They fit on the skin with shred, these tiny pieces of skin, and the mold or fungi that grow on this. Under my body, I capture mainly the families called pyroglyphidae, like dermatophagoides mites, that are the most common and worldwide distributed houseless mites. And around my body, towards the borders of the bed, you find the predators that feed on these mites. So they are like patrolling the... And we also carry them on our clothes. If we are wearing for a couple of days the same clothes, we start carrying the mites. And we carry both, the preys and the predators. And I also tape my clothes.

19:16I carry clothes for three, four days. And actually, I use very dark clothes on purpose. So in my clothes, I found the same mites I found in the bed linen. I found the preys, the same species, and the predators. These predators, sometimes, you are talking now with me, and suddenly you feel something like a puncture or something that bites you in your skin. You touch or you look at it and there is nothing. And it's very likely one of these mites because they are so tiny you don't see them. And they sometimes puncture you because they get thirsty or something like that. and it's just the Keiletidae is the name of the family Keiletidae mites So why is it that some people react really badly to these mites that are in your bed or in your pillows, whatever and some people don't?

20:11Because they are sensitive, they are allergic to them it's all related to the immune system Right, and what about the kind of mites that cause real issues whether you're allergic to them or not so things like scabies and lice Okay. Have you studied those at all? Yes, I work on them. So you have some that are really pathogenic, if you want. They are parasites that cause problems, especially scavis. Scavis is Sarcoptes scavei, it's a species. The female makes tunnels, digs under your skin. Actually, all the offspring spreads under the skin. For example, to mate, it has to go to the opening of the tunnel to mate.

20:57The male will mate through the opening. The most difficult to treat is the females, because the females are the ones that are reproducing, making the tunnels and spreading all the offspring. It's extremely itchy, and there are different varieties depending on the host, but it's always the same species. So the same species can go to humans, to dogs, to cats, to horses, to sheep. They do really disasters when they go to wildlife, because wildlife, the first time they colonize or parasitize a new host species, they are very aggressive. Why are they so aggressive when they kind of jump to a new host?

21:46I think because, well, the new host has to develop the immune system to resist this and didn't give time to it. From a biological point of view, what do these infestations actually signal? So if I get scabies, what does that say about how my body's responding? In humans, in dogs, if the host is immunocompromised, in cases of neglect, for example, where the person, if we are talking about a human, the person needs to be taken care of by somebody and is abandoned, is undernourished. In these cases, they can get scabies and develop scabies in most of the body. It's extremely nasty. In general, it happens in children, toddlers, babies, and in elders that are neglected or abandoned or living in the streets.

22:52People living, homeless people, for example, have scabies. The same for lice. You have extreme cases of pediculosis in people that are homeless or neglected. Yeah, so it's actually very sad. It's not about, you know, dirtiness. No, not necessarily. It's about malnutrition. A person with depression, for example, the moment the immune system gives up, they come. Alejandro, if there's one thing that you wish people would understand about living with mites, what would that be? Well, yes, that they are never alone. Very comforting though. Yeah, it's just you go back in the night and if you're alone, you say goodnight, have a good evening to your mites, looking at the screen, at the mirror, and you are never alone.

23:55That's beautiful. That is beautiful. You've converted me. After our conversation, now I am a Demodex lover. So thank you. Welcome. I'm Gemma Ware, host of the Conversation Weekly podcast. Each week, I speak to an academic expert about a topic in the news to understand how we got here from global politics. World War II has this very long shadow in all of East Asia because there's a lot of unfinished business. To the latest scientific breakthroughs. The drug has been shown in real world environments to be highly effective at preventing HIV. All the big dilemmas facing our planet. We have actually stumbled in the last few decades into a system where those products that we rely on for the economy to be sold every day are pollutant and they're polluting things very badly indeed.

24:42My guests draw on their deep research knowledge to pull out what really matters so that you can understand the context without the spin. Follow The Conversation Weekly for new episodes every Thursday, wherever you listen to podcasts, and read more stories direct from academic experts every day on theconversation.com.

25:05I thought she was brill and really funny. Absolutely amazing. I tried to make mates with her and suggested, you know like oh let's go for a coffee and she said um well yeah I'll I'll stick some tape to your face and see how many mites are on there and I thought uh yes sees me very much as a as a study I I understand very much very much as a very much as a case study but I have to say because she was really loving she'd got a lot of a lot of demodex love um so I wanted to pretend that I was really cool with it as well and like it was all good but then she was telling me about um having sexy time on your face at night i don't want to think about that like if they live on me like fine you know i'm a walking ecosystem that's brill yeah but i don't want to think about um doing the bits don't want them getting jiggy with it on your face no most certainly not and what a marvellously niche area to end up in as well have to say to be an expert in demodex these little tiny mics that most of us are not unaware of.

26:08So I was talking to Alejandra about scabies, which is getting loads of attention at the moment because there's currently a surge of cases in the UK and Europe. Now, Dan, you work as a GP. You must have seen scabies a few times. Yeah, many a time. And as for the sort of the rising cases, you're absolutely correct. GPs and dermatologists have been seeing more cases than usual, including outbreaks in care homes, schools and student accommodation as well. So Dan, how do you know it's scabies and not something like eczema? Well, I think the main thing that we ask about, or what main thing that the patient would present to us about is itching.

26:48And itching is one of the cardinal symptoms of scabies. I've never seen a case of scabies where someone hasn't been harangued by itching because it's so intensely itchy. In fact, the literal meaning of scabies or being, you know, scabrous is to be itchy. In fact, that was what defined it back years and years and years ago, back in the time as it was possibly documented as early as ancient Egypt, because of this intense itching that really, really plagues you. So it is a bit like an Egyptian plague. It's sort of written back in the annals of history. And of course, we know that itching can come from lots and lots of different medical conditions.

27:28Eczema can cause itching. But then you need to try and put the pieces together a little bit more and try and work out what's causing this itch. Sorry, I've got a footage now. And this immediately makes people anxious, doesn't it? Because scabies also carries this huge amount of social baggage with it. I mean, the mite itself is not due. I remember at school, when people got scabies, they were horribly bullied for it. And it's not right, is it? That stigma is completely and utterly misplaced. So from a medical point of view, scabies doesn't tell you anything about hygiene at all. It's not about being dirty.

28:07In fact, most mite and lice disease is not about being dirty at all. It's about the contagiousness of certain things. And actually, scabies, you do need to have fairly prolonged contact with someone. It's not sort of like brush past someone with scabies or walk within 10 feet of them and the mites will jump from there on onto you. It's not as contagious as that. But when you do get it, for whatever reason, you need to take it seriously and you need to treat it before it becomes more of a problem. So how do you treat it then? So actually scabies is really very treatable. And the treatment that we use is a topical cream or lotion.

28:42There's a variety of different ones, but there's one which is readily available from the pharmacy. you apply it to the whole body from the neck down sometimes the scalp as well in elderly patients or young children and that's simply because they're a little bit more prone to getting it elsewhere not just on the body but most cases it tends to be on the body so we say apply it from the neck down in the instance of the one that i'm thinking of which is permethrin it's usually applied overnight left on overnight so you have it on your skin for a couple of hours and then washed off the next day. But the most important thing is that it's repeated a week later.

29:17Right. So that second treatment really matters then? Yeah, absolutely. It does. The first kills the mites. The second catches any that might not hatch yet because we're going back, sorry, going back to that thing of hatching eggs. Some of the eggs are still in the skin and they haven't hatched out yet. And missing that step is often the reason sometimes that scabies doesn't clear properly. And sometimes actually scabies can progress if it's been left a long time into a more contagious form where you shed larger numbers of mites so the mites start to proliferate more and you can shed more mites from sort of skin flakes which come off the skin when you scratch oh can i feel a case study coming on dan so yeah always come prepared with a case study so what we're talking about here in this more contagious form is a nasty and more severe form of scabies which was first read back in 1848 by doctors in Norway.

30:07And the twist is they weren't actually looking for scabies at all. They were studying people with leprosy. And they examined a patient in whom the skin was really, really thick and crusted. And everyone assumed it was some sort of leprosy variant. And it took a while for them to realize it was actually scabies and just scabies that had caused a skin reaction to the extreme. In fact, it ended up being called Norwegian scabies, purely because the doctor described in the first instance was Norwegian. It had nothing to do. There's no... Norwegians don't have an increased risk of developing scabies at all.

30:40These days, it's usually just called crusted scabies, which is a more accurate term and avoid pinning it down to a place unfairly. Top trivia, Dan. I bet you're a right laugh at pool quizzes, aren't you? Oh, well, provided it's not the sport round. Film a science, I'm your man. But sport, I'm afraid you have to rely on somebody else. So with the trivia for scabies then, is there anything else that you need to do? Everybody in close contact needs treating as well, even if they're not itchy yet, because the rash can take several weeks to appear. Probably the most onerous thing is not actually putting the lotion on.

31:10It's to, unfortunately, wash all your laundry, both clothes and bedding, anything that's come into close contact with you. And the thing is, on a hot wash as well, you need 60 degrees or more. All that heat is what's going to kill the mites and their eggs. And if you've got one to hand, a tumble dryer afterwards, eradicates any mites or eggs that may have made their way onto the clothing. And that's really important because otherwise you'll transfer the mites and the eggs back onto you. What about lice then? Because people often lump them in with mites. And at school, again, I mean, as I'm talking to you, I realise that we were, right, nasty little things when we were at school.