Hello, my name is Steven Munger and I am the Director of the University of Florida Center for Smell and Taste. My research focuses on understanding how we detect and respond to odors and tastes, AMA!

Abstract

Hello, Reddit! I’m Steven Munger and I’m fascinated by how animals, including humans make sense of the chemosensory world…everything from how smell and taste influence which foods we choose to eat, to the influence of odors of social interactions between individuals, to the impact of smell or taste loss on our health and quality of life.

A bit of information on me: I’m a Professor and Vice-Chair of the Department of Pharmacology and Therapeutics and the Director of the Center for Smell and Taste at the University of Florida.

I received a BA in Biology from the University of Virginia (1989) and Ph.D. in Neuroscience from the University of Florida (1997). I completed postdoctoral training in molecular biology at Johns Hopkins University before joining the faculty at the University of Maryland School of Medicine in 2000, where I remained until joining UF in 2014.

My lab focuses on understanding the molecular and cellular machinery used to detect odors, tastes and other chemicals in foods and pharmaceuticals. But I am looking forward to questions on any aspect of smell or taste!

I'll be back at 1 pm EDT (10 am PDT, 6 pm UTC) to answer your questions, so ask me anything!

***Hello, everyone. I am glad to be back this year for another AMA about smell and taste. I'll be online for a couple of hours this afternoon, and then will try to get back to answer some more questions later this evening. I'm happy to try to answer questions about all aspects of smell, taste or chemesthesis (the chemical sense that allows us to detect chemicals in herbs and spices that evoke a sense of temperature, irritation, pain or vibration). And questions don't have to be limited to humans, either....smell and taste are important senses for all sorts of vertebrate and invertebrate animals.

I did want to take this opportunity to mention that we recently announced the launch of the UF Health Smell Disorders Program, which will provide patient care, education and support for those with smell impairments as well as focus research on anosmia and related disorders. For more information, you can visit http://smellclinic.cst.ufl.edu or ask here.

And with that...let's get started!

***I am going to have to leave in a few minutes (I will try to get back to answer the remaining questions later), but wanted to make sure to add a few important points:

--As you see from my bio, I am a scientist, not a physician. If you think you have a smell or taste disorder, you may want to visit an otolaryngologist or other physician with experience diagnosing these disorders.

--For more information about smell disorders, visit http://smellclinic.cst.ufl.edu. This website contains, among other things, a list other organizations that may provide you with useful information about smell and taste. For example, the UK-based charity Fifth Sense (http://fifthsense.org.uk) has a number of resources for those with smell disorders. They are also holding a members meeting in Leeds, UK, next month. This can be a good way for those with a smell or taste disorder to learn more and to connect with others with similar experiences. UF and Fifth Sense will also be partnering for SmellTaste2019, a patient focused conference to take place in Florida in early 2019.

***OK, I actually was able to answer everyone's questions. If you have more about smell or taste, you should look at my two past AMAs on the subject. Thanks for your interest, and good night!

Hi Steven! Thanks for your AMA. Ill be honest, I don't know much about odors and tastes. My question is, what is something really interesting about odors and tastes you want everyone to know?

im-a-grumpy-old-cat

Glad to be here. I'll give you one important fact, and one that fits your username. The important fact is that smell and taste disorders are incredibly common. While it is difficult to get specific numbers, good estimates indicate that up to 15% of the population has some sort of smell or taste impairment, whether that be reduced smell (hyposmia), complete smell loss (anosmia), distorted smell (parosmia), phantom smells (phantosmia), or their taste equivalents (-geusia instead of -osmia).

The cat-related fact is that cat's (and other carnivores) lack an intact gene for a critical component of the sweet-taste receptor. Thus, cats con't taste sweetness.


My friend loves coriander. I absolutely can’t stand it. Why do some individuals taste some foods so vastly differently? More so than what you’d expect from personal preferences

Nihil_am_I

Coriander (also known as cilantro) is one herb that can elicit very different perceptions. For some, it has a grassy, minty smell, while for others it is very soapy. This difference has been genetically linked to a mutation in one particular odor receptor. The idea is that if you have a non-functional (or reduced function) version of the receptor that normally recognizes the compound, you are left with only being able to detect part of the aroma (which is less appealing without that "top note"). Think of it as the difference between a full guitar chord and one missing a key string.

But preferences can also be dramatically shaped by your experiences, motivations, etc. dietary preferences across cultures is a great example of this.


Do you consider olfactory evoked potentials a useful tool for any real world diagnostic problem?

ALR3000

I am not sure I fully understand the question. But to my knowledge, olfactory evoked potentials are not typically used to diagnose olfactory function.


Hello there, Steven! Thanks for volunteering in an AMA today. I wonder if my question could be in your field so that you could give an opinion. Context: I have idiopathic anosmia. I was wondering if there is any evidence to support that issues besides weakened taste have been attributed to smell (I.e. behavioural issues or weakening other senses), or if you have any personal theories. Thank you, in advance.

Synchronea

Thanks for this question. For those not aware, "idiopathic anosmic" means that there is smell loss but the cause is unknown.

Typically, taste per se is unaffected by anosmia. Rather, what most describe as diminished taste is actually diminished flavor perception. For example, if someone with anosmia puts pure sugar or pure salt on their tongue, the can still detect it normally. What is missing is the odor contribution to flavor.

Flavor happens in the brain, where taste and smell information are put together (along with temperature, texture and other information) to give you a fuller perception of the food or drink you are consuming. Part of the reason that taste and smell are combined in this way is that they are detected at the same time...odors released from the food or drink in your mouth travel through your throat and into your nasal cavity, where they can activate olfactory (smell) sensory neurons.


How differently do we perceive tastes than animals? Is there a link between our closeness to them(based on families)?

useful_person

It is a tough question to answer because we have to infer how a non-verbal animals perceives a taste from their behavioral response. That being said, most animals find sugars (which we find to be sweet) to be highly appetitive (that is, they like consuming them). But many lower mammals are indifferent to some natural and artificial compounds that we find to be sweet (such as the sweetener aspartame or the sweet protein monellin) because these compounds don't activate their version of the sweet taste receptor (which is related, but subtly different, than ours). And, as I mentioned elsewhere, carnivores typically can't detect any compounds we find to be sweet because they lack an intact sweet taste receptor.

Similarly, bitter-tasting compounds are generally aversive, and sodium salts are appetitive at low concentrations (such as on potato chips) but aversive at higher concentrations (such as in sea water, which can kill us if we drink too much).


What causes extra sensitive smelling? I'm like a dog, I catch all smells and differentiate and identify them. Also, is my chronic nausea (I do have Crohn's, so that could be it) caused by smelling everything involuntarily or are smells heightened by the nausea?

kederam

Unfortunately, we don't really know why some people seem to have a heightened sensitivity to smells. One could think of several potential explanations. Analogous to super-tasting (hypergeusia), it may be that some people are just generally more sensitive, perhaps due to a great number of sensors. It could be a difference in the brain by which you are more attentive to smells than are other people and thus are more likely to recognize and respond to them. Or it could be a form of parosmia, where odors trigger a distorted smell perception.

I am not aware of a link with Crohn's, but that could be my ignorance.


do you know some stories about fart research?

howardCK

No


What's the worst thing you've ever had to smell?

Professor_Crab

Fairly concentrated isovaleric acid is pretty bad. Cadaverine is also not pleasant.


Hi and thanks for joining us today!

I'm a bit of an espresso junkie and am always chasing that perfect shot. Can you explain how a perfectly balanced shot of espresso can actually be quite sweet on the palate whereas even slightly off it can be quite bitter/acidic?

Also, your professional opinion as a chemosensory expert, is coffee or tea the better drink?

PHealthy

A bit out of my expertise here, but I don't think there is anything unique about espresso in your question. Especially as we get older, we often find that balance and complexity are hallmarks of the best food and drink (children are more prone to enjoy something that is purely sweet, or to avoid something, like coffee, that has a significant bitter component).

Personally I am a coffee drinker, but there are some complex and interesting teas out there, too. So, I will vote: beer.


Thanks for your time, Steven! My question: how do people "acquire" tastes? Many people and animals would turn up their noses at fermented foods and beverages, or even hate the taste on a first experience, but eventually fall in love with them. Even in a more mundane example we have things like kids not liking vegetables. What can you tell us about this process of changing tastes?

Takenabe

I think the important thing here is to first define "taste." For clarity, I will try to always use it as an equivalent of gustation...that is, the detection and perception of chemicals in the mouth that elicit perceptions of sweet, salty, bitter, sour or umami. In your question, you are really talking about preferences (and particularly, preferences for specific flavors). Taste is largely innate. Babies will prefer sweet and dislike bitter. But as we go through life we put flavors in the context of other experiences. We start to enjoy coffee or beer, even though these drinks have significant bitterness that should tell us to stay away (many plant toxins, including cyanide and strychnine, taste bitter). Why? Because we associate those flavors with things we prefer, including the buzz of caffeine or alcohol, the other flavor components, or the social situations in which we drink them. All of those things can impact taste preferences. With the example you give of kids and vegetables, research shows that early exposure increases acceptance and liking later in life (positive context would likely help, too).


How can we digitally store smell? Or just accurately record aromas as information.

SagePlox

Aromas are mixtures of chemicals. If you can determine the exact chemical composition of an odor (including the relative amounts of the chemical constituents), then you should be able to represent that odor digitally. Indeed, flavor companies are now very good at determining the composition of an odor mixture and recapitulating it.

However, it is important to keep in mind that how an odor is perceived can differ between individuals depending on their genetic makeup (do they have certain key odor receptors that are mutated) and maybe their olfactory health.


Hello Dr. Munger. Thank you for this AMA.

In dealing with wildlife, I've noticed differences in reactions to taste and smell of medications. For example, of the handful of bobcats receiving treatment on a daily basis, half will gladly eat the piece of mouse containing their medication with no hesitation. Another will expertly eat around the pill, while two others seem to smell which pieces have the medication and avoid those pieces completely (until we provide something more enticing, of course).

I'm curious, what accounts for the range of individual differences in preferences among the same species as far as what they will consume? Does either sense (smell or taste) have more weight when the individual makes their determination?

edit: a word

chupacabrasaurus1

Our dogs have a talent for this. Very annoying.

Just like with humans, other animals can have differences in olfactory ability (due to genetics or olfactory health), differences in taste ability (for example, there are many known mutations in bitter taste receptor genes, some of which can impact the ability to taste certain compounds), as well as differences in experience. Let's touch on the last two since I haven't discussed them as much in earlier posts.

Many medications have a bitter taste because one or more of their ingredients activate one or more bitter taste receptors (humans have ~25 of these receptors, compared to only one sweet receptor). If an animals has a mutated gene for the receptor that would respond to the compound in the medicine, they would not taste it or perceive its bitterness.

As for experience, let's assume the animal can taste the bitterness in the medication. If they taste it one time, they may learn to associate that aversive bitter taste of the medication with its smell. Thus, next time they smell it, they will know to avoid it.


Hi! I had a cold about 6 months ago and since then, I can't smell very well. Any idea how or why this happens and will it get better?

Jeremiahjohnsonville

I am sorry to hear about your smell loss. Some smell disorders are thought to be "post-viral." That is, a viral infection associated with a cold, flu, etc can cause damage to the olfactory sensory neurons in the nose and impact smell function. The potential good news is that spontaneous recovery can happen from post-viral hyposmia (much more often than smell loss after head trauma, for example). However, the reality is also that the time frame can vary and there are no guarantees that recovery will happen. There aren't any treatments for post-viral smell loss, but you may want to consider visiting an ENT knowledgeable about smell disorders to make sure that you smell loss is not due to something else.

In the meantime, there are things you can do to make your house safer and to enhance your quality of life (adding textures and spices to food, engaging with others with similar experiences). The UF Health Smell Disorders Program website has a number of those resources available, and we will continue to add more. Best of luck.


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[deleted]

For humans, the identity and meaning of smells are learned, not innate (other animals can have innate responses to some odors, such as those functioning as pheromones). A great example is durian fruit, which some find to smell horrible but others, who have grown up with it, can find appealing.


hi there, thanks for giving up your time for this!

i was wondering, could you shed any light on why different people experience tastes very differently?

and also why it is that one can like the smell but hate the taste of something? for example, i love the smell of coffee but cannot stand the taste.

really interesting field, i'm glad you could be here today

TrivialBudgie

You are welcome.

One quick clarification...the difference between taste (the detection and perception of chemicals in the mouth that elicit perceptions of sweet, salty, bitter, sour or umami) and flavor (how your brain perceives a food or drink based on a combination of its taste, smell and other sensory attributes).

It is not unusual for people to like a smell but dislike the flavor of something. This may be in part because of of the different contributions of a smell and taste (the smell of coffee lacks the bitterness that is part of its taste), or perhaps due to the context and your experiences (the smell of coffee signals a new day, or the presence of others in your house). For both smells and flavors (but less so for tastes specifically), context and experience are very important components for determining whether you view them positively or negatively.


I've always heard that women have a better sense of smell than men. However, I've got the most sensitive sense of smell than anyone I know. Is there an explanation as to why some people have a better sense of smell than others? Is it genetic or is it a simple as some people take the time to experience and associate smells with memory while some don't?

Azozel

I am not sure how robust these differences actually are, but you should keep in mind that they reflect differences in average sensitivity. So, some men will be much more sensitive than most women, and some women much less sensitive that most men. Some relevant data I am aware of suggests that age-related smell loss is faster, or is more pronounced, then men.

The apparent close relationship of odor and memory is largely anecdotal, I think. However, one potential explanation for why odor-triggered memories are often described as particularly vivid and detailed may be the close proximity of olfactory areas of the brain to those that are important for memory formation and consolidation. But this is speculative.


Why am I able to vividly remember a smell or taste if I think about it and inhale (if there is no other smell present)

Misery_101

I don't know. It is not something I can do, and many would claim that this is a much more difficult task than conceptualizing a visual memory. You may just be particularly adept at this.

I should note that this is a bit different than a talent often associated with chefs, perfumers, etc....the ability to recall many specifics about a smell when exposed to it (such as when they last smelled it, the ingredients it represents, etc).


What is your general outlook on human detection and responses to pheromones/chemosignals? How does this differ from plant-based essential oil aromatherapy?

Disclaimer: I am the founder of a company called Pheros, which investigates products in that space- particularly TAR.

ThomIvy

The evidence for human pheromones (odors given off by one member of a species that evokes a behavioral or hormonal change in another member of a species) is quite weak, to be generous (I suggest reading the work of Tristram Wyatt for more on this subject). Indeed, the most common pheromone sold for human use is actually a boar pheromone (which most humans probably don't want to attract). Evidence for aromatherapy (odors eliciting specific health effects beyond just pleasantness) is similarly lacking. Thanks for being upfront about your association. I am afraid I have no confidence that the underlying concept is valid in humans.


Why is it that we no longer smell something if we get used to the smell? Wouldn't this cause a huge survival problem in nature?

For example when I spray eau de toilette of a certain brand, after a few weeks I don't smell it anymore myself, while others still can. Then you switch a few weeks to a different smell and back, and all of a sudden the sent is strong again.

Or am I just imagining this?

ecky--ptang-zooboing

Adaptation (or habituation....closely related concepts that somewhat depend on where you are measuring the response) is actually quite valuable. The idea is that new smells are going to be the most important, whether it comes to finding food, finding a mate, or avoiding danger. You want to ignore those smells that have been around you for a while so that you have the ability to attend to what's new.


Hello, is there a word or phrase for something that tastes like something else smells?

For example when drinking a bourbon people often say "That has an oak taste" but Noone really eats oak, its more of a sense comparison.

Thanks, I have always wondered about this.

bigoted_bill

This confusion is quite common, and it comes from the fact that most people use the word "taste" to connote either taste itself (sweet, salty, bitter, sour, umami) or flavor (which comes from your brain combining taste and smell information, often with other sensory info). In the case of bourbon, much of the flavor does come from the oak in which it was aged, but these are volatile compounds that you detect as odors. The taste of bourbon is largely its subtle sweetness. The alcohol may have a taste, as well, but all acts as a chemesthetic agent (the same way capsaicin in hot chili peppers or menthol in mint are detected).


Why are people obsessed with smelling gross things? Some people will smell their own flatulence, or someone will say, “This smells nasty, come smell this!” and we’re immediately curious WHILE continuing to smell it.

Also, what is one of the worlds most flattering fragrance that everyone loves?

KnightDivine

To your first question, I am afraid I do not know.

To your second question, my guess is that what fragrance is most flattering will depend on your own body chemistry. You have your own odors, and you would want to complement those with any added scent.


How much do we know about olfactory hallucination? How often does it occur and what causes it?

BravesMaedchen

Phantosmia (phantom smells) can have a variety of causes, but there isn't a lot of work done on understanding them. I would break the causes into three groups. Some seizures, such as experienced by some with epilepsy, can evoke olfactory phantoms. Peripheral damage to the sensory cells in the nose that normally detect odors can lead to phantoms, perhaps because the sensory cells are still alive but are randomly misfiring. Damage to olfactory areas of the brain could lead to phantoms, perhaps if areas important for odor perception mistakenly think that they are receiving input from the nose.


This has always been something of a debate between myself and family. I've never really had a sense of smell due to a childhood illness. I still enjoy food and I think I can taste differences in stuff pretty well. However half my extended family thinks I'm bluffing.

How much of my thinking is actually correct?

leebd

Smell loss (whether partial or complete) is very common and definitely impacts the way you perceive food. Many with a smell disorder find food very unpalatable, while others are less negatively affected in this way. Getting an olfactory assessment from an ENT with relevant experience and the right tests would be one way to quantify your olfactory function.


My Q is about food poisoning. Is there some odor/taste that is detected but not conscious untill you are puking/pooping it out?

My internal monologue when I got food poisoning was:

Eating: ‘everything is delicious!’

Vomiting: ‘it must have been the crab!’

I’ll take and fun taste/odor food poisoning facts off the air. Thank you.

pacmanman

Conditioned taste aversions (or conditioned smell aversions) are very common. You eat something and it makes you sick...the next time you smell or taste it, you feel ill even if that food is perfectly fine. There are interesting studies showing that the brain actually changes the way the taste is represented. If you make a rat sick while it eats a sweetener, the rat's brain will then represent sweet and bitter tastants similarly (though they were differentially represented before the experiment).


Hello! Thank you for doing this! I work as a sommelier and I'm interested if there are any ways to improve the sense of smell (other than the obvious like not smoking etc).

I am super passionate about wine, but I don't have a particularly keen sense of smell which limits me somewhat (noticed this over a long period - compared to my peers I need to be closer to something to smell it, other people always notice smells first, etc). Through lots of blind tasting my palette has improved and I'm better at 'recognising' aromas, but my nasal "hardware" is somewhat holding me back.

Again, thank you!

smallerthanhiphop

The most important skill for a sommelier or other professional that deals with smells, tastes or flavors is to do what you have already accomplished....develop you palate (which just means become more adept and recognizing and remembering different flavor components). There is no clear way to improve your nose's ability to detect smells unless you have a treatable medical issue that is inhibiting the ability of odors to get to your sensory neurons (nasal polyps, some physical disruption of the nasal cavity, chronic sinusitis or serious allergies). If you suspect any of these, a visit to an ENT may be warranted.


Hi Steven. Thanks for the AMA, I am already seeing lots of interesting questions and can't wait for your responses. Anyway, my question.

We often say that dogs have a much better sense of smell than humans, how true is that and how do you determine it?

For example, can you measure the minimun amount of particles in the air until someone is able to smell something? Or is there any specific biologic response you look for?

mecharri

Dogs definitely can respond to parts of the olfactory world that we ignore (for example, their use of odors for social communication). And, dogs are more willing to put their noses right in an odor source, which helps (for example, if you get down on the ground you could follow a scent trail, too). However, the idea that dog's are more sensitive to general odors is not the case. Indeed, testing with a variety of odors shows dogs are more sensitive to some, humans to others, and for others they are similar.

These types of measurements can be made using a variety of techniques, but in many cases an olfactometer is used...these instruments provide an odor at several different defined concentrations, and responses are measured through a trained behavioral response (or in the case for humans, making a selection on a computer).


There's a company that sells a Super Taster kit that they say can determine if you're a super taster or not. Does that sound like it could be a legitimate test?

Do you have overall opinions on the concept of 'super tasters'?

moocowrich

It is basically legitimate, but usually misused and misinterpreted. These kits contain filter paper impregnated with either of two bitter tasting compounds (known as PTC or PROP). One problem is the concentration is generally higher than it needs to be. But there are two additional complications.

1) A large percentage of the population is incapable of tasting these compounds (or related ones in Brassica vegetables) due to a common set of mutations in one bitter taste receptor gene. These people may still be super tasters, but the test can't determine it because they are PROP/PTC-nontasters. A different compound would need to be used.

2) If you can taste the compound, is it bitter and unpleasant, or does it taste like possibly the worst thing you ever stuck in your mouth. If the latter, you could be a super taster (also known as hypergeusia).

Perhaps the best test for super tasting is using a blue dye to stain the tongue and then counting the number of taste papillae (the larger bumps). Super tasters have many more, which is probably why they are more sensitive to various taste stimuli.


Will it possible to simulate smell in the near-medium term future for virtual reality?

I'm talking direct olfactory stimulation without real scents but instead fooling the brain with stimulations that simulate them. Is it theoretically feasible?

Chispy

I am guessing it is feasible (we are getting a better idea of how the brain encodes odors, though this work is largely done in rodents), but one challenge would be accessing the olfactory brain non-invasively....it largely lies on the underside of the brain behind the eyes.


My question: Do you do tests to see if people with mental disorders experience taste and smell differently than people without disorders? Like autistic people.

Jesteress

Unfortunately, smell and taste disorders are often ignored as many might consider their impairment less important than other issues for a patient (for example, epilepsy, schizophrenia, brain tumors). Of course, as smell and taste function can have such a dramatic impact on eating (and thus nutrition), I would argue they should not be ignored and deemed unimportant.


Have you thought about trying to create a large database of people's taste preferences related to genetic markers, to possibly identify more genes like TAS2R38 in "supertasters" that relate to sensing specific flavors or scents?

zajhein

Smell and taste scientists are slowly building this type of database, though it has been slow going (a combination of the poor state of science funding over the last decade or more, and some technical challenges working with odor and taste receptors). A few have been found by academic scientists, and a few others by private companies.

I should note that TAS2R38 variants are not directly related to being a super taster....it is just that common stimuli for that receptor have been used to assess super taster status (something that doesn't work for TAS2R38 non-tasters)....see my other answer on this subject above.


I met a man the other day who claimed to be 'nose-blind' as in he could not smell. What would cause this? A tongue has taste buds, but what do we use to interpret smells?

(Sorry, I obviously know nothing about how smelling things works)

FishFeast

Anosmia (the inability to smell) is actually quite common and is far from trivial for those who experience it. Causes include genetic mutations, head trauma, blockages (such as nasal polyps), chronic sinusitis, serious allergies, viral infections, inhaled toxins, tumors, epilepsy, and neurodegenerative diseases. Anosmia can impact safety (detecting spoiled food or gas leaks), eating (flavor perception is severely impacted), social interactions (not being able to smell your baby or your partner), and connections to the world around you (smelling the first flowers of Spring, or fresh fallen snow).


How exactly do we smell? Is everything releasing some type of radiation or something that we pick up with our noses?

Yellowjo

Odors and tastes are chemicals. In the case of smell, the chemicals are volatile and float through the air. They reach specific neural sensors in our nose when we inhale, which initiates a signal to the brain that we perceive of as an odor. What those signals mean (cheese pizza, rotting fish) is something we learn through experience.


Hi Steve,

I was wondering if you have ever figured out why and how age seems to have varying impacts on tastes but as well or potentially smells.

vogt18

The sensory cells in the nose and in the mouth that detect odors and tastes, respectively, die throughout life and must be constantly replaced (this is likely because they are constantly damaged by the things we inhale and ingest). Just as the rest of our body becomes less able to repair itself as we age, it appears that the capacity of the sensory tissues for smell and taste become less able to replace the dead cells.


Hi Steve, I currently work in Incident Management for the Coast Guard, which is mostly environmental compliance. One thing we learn about in safety training is olfactory fatigue, particularly when it comes to hydrogen sulfide. My question has two parts: what is the purpose (if any) of olfactory fatigue, and why does our sense of smell basically stop working when - in some situations - it may be our only way of detecting danger? Thank you!

coastal2000

I'll copy an answer to a related question I gave earlier.

"Adaptation (or habituation....closely related concepts that somewhat depend on where you are measuring the response) is actually quite valuable. The idea is that new smells are going to be the most important, whether it comes to finding food, finding a mate, or avoiding danger. You want to ignore those smells that have been around you for a while so that you have the ability to attend to what's new."

But you make an important point here....sometimes you want to be able to maintain awareness of an odor, especially one that may represent danger. This is one place where specialized chemical sensors (e-noses) could be particularly valuable.


Hi! Thanks for this AMA, my question relates to the development of smell, my family member had severe nasal polyps throughout all sinuses as a child which were at some point removed but returned quickly, he essentially has no sense of smell. I'm wondering if the olfactory bulb is obstructed or ethmoid sinus/ cribriform plate is obstructed (in this case by polyps) if you never develop smell early on, would you be unable to "learn" smells later in life? (with obstructing polyps removed) Thanks again!

clh08h

It really depends on where the obstruction is, I think. You are correct that if the olfactory nerve can't pass through the cribriform plate then that may be very different than if air just can't get up to the sensory neurons in the first place.

Nasal occlusion studies have been done in rodents to investigate in impact of losing odor stimulation for long periods of time. There usually is functional recovery after this surgery (though it is typically done unilaterally).

The best I can do is to recommend that your family member explore having the polyps removed now.


I'm an extremely picky eater due to some food related trauma when I was very little. Is there anything that can be done to trick yourself into liking different tastes, or any other tips you might be able to give to someone in my situation?

alistious

I want to be careful here because I am not a psychologist and have no experience with trauma therapy. However, I would say that learning to like the flavor of any food when it is not inherently appetitive (such as sugar) often involves associating that flavor or that food with something else you like...friends, family, a particular experience or cultural touchstone. Flavor preferences are learned to a great extent.


I have an absolute terrible sense of smell but can still taste fairly well. What gives?

More details: I can smell some things but by the time I notice them, most other people consider the scent to be practically unbearable. Nothing ever happened to "tone-down" my sense of smell. I just slowly realized I suck at smelling and always have.

ValdyrDrengr

One potential explanation is hyposmia (reduced ability to smell), which is a common smell disorder. In some cases (nasal polyps, chronic sinusitis, serious allergies) this may be treatable. You may want to consult an ENT with experience diagnosing smell disorders.


Is there something in blood that makes animals want it or am I just weird?

Followup:Do they only associate the blood with meat and that's why?

LeviathanX000

Animals will be attracted to odors that indicate the presence of something they want/need (food, a mate, etc) and avoid odors that indicate something to avoid (predators, etc). For animals that eat meat (carnivores, omnivores), they have probably learned to associate the odor of blood with the presence of food.

Interestingly (at least to me) some animals are thought to give off odors (known as alarm pheromones) when injured or dying. These odors (not clearly identified) can induce avoidance behaviors in other animals of the same species that detect them.


Dr. Munger, thanks for doing this AMA. I'm personally interested in this topic as I've had some odd things going on with my sense of smell for the last couple of years.

Specifically, my sense of smell is normal every morning when I wake up, but then, on most days, I have an abrupt alteration to it. It tends to happen with I breathe in deeply or blow my nose, and it also seems to be triggered on one specific side.

I've had a CT scan of my sinuses that shows nothing unusual. Also, it's not a loss of smell, just a change. It most affects coffee, chocolate, and bacon/meat type smells, making them more bitter and/or metallic.

Just curious if you'd ever heard of anything similar and if there were any potential treatments my ENT may not have considered.

Dirtman1016

Once again, I am not a physician and do want to be making internet diagnoses. That being said, some of your symptoms resemble those associated with parosmia, a disorder of distorted (changed) smell. At the SmellTaste2017 conference this past February, several attendees with parosmia noted that chocolate was a particularly potent trigger.

Parosmia can have a variety of causes, and can be associated with reduced smell, chronic infections and neural damage. Similar to suggestions I have made for others, you may want to consider visiting an ENT or neurologist knowledgeable about smell disorders to see if there may be an underlying problem that was missed before.


A very good friend of ours has Alzheimer's. We've noticed that she can't smell much, if anything. She also doesn't have much of an appetite and so is underweight. I don't know how much she can "taste." Is there anything one can do, given this limitation, that would increase one's taste and therefore appetite, or is smell the keystone for taste? (I'm not asking for medical advice.)

fahrnfahrnfahrn

Unfortunately, smell loss is yet another negative aspect of Alzheimer's. As you noted regarding your friend, this can result in diminished appetite. One way to make food more palatable is to engage the other senses. Adding texture can make a big difference, as can adding herbs and spices that activate the trigeminal nerve (part of the third chemical sense, chemesthesis). Even temperature changes can make a difference. But it is probably best to try out a number of options to see what is most appealing to your friend. For example, while some people with anosmia add hot sauce to all their food, others find hot sauce or other strong spices.


Thanks for your time! I've heard of the Odor Threshold Value, but is there a threshold at which the smell becomes so concentrated it's repugnant/hard to breathe?

(and is there a name for that level of concentration?)

OmgHomology

In the context of odors, the term threshold just refers to the concentration at which you can accomplish something related to that odor at least 50% of the time. So, detection threshold (you know an odor is there), recognition threshold (you can identify the odor), etc. And of course, these concentrations will vary across individual odor chemicals for a variety of reasons.

I don't know if you would put a label on a concentrations at which an odor is becoming unbearably noxious. If you find it horribly repugnant, that will be impacted by learning (someone who grew up on a farm will have a very different feeling about the smell of manure than will someone who did not). If the odor is getting hard to breathe it may be because it is engaging pain or other trigeminal receptors in addition to odor receptors.


Is there a reference to find odor threshold values for chemicals of common smelly foods, like garlic AMS and vinegar?

OmgHomology

Not that I know of, and it would depend what kind of threshold you are talking about.

For both of these, the noxious component is likely trigeminal, not olfactory, as well.


Thanks for coming to talk with us today! Is there any research on homeopathic nose washes and sprays that can damage your sense of smell? I used a lemon-based nose wash (recommended by my ENT for chronic sinus infections) which I believe may have damaged my sense of smell. Is that possible?

asbruckman

Several years ago, a popular brand of homeopathic nose spray was removed from the market because it was causing smell loss in a large number of people. It contained zinc, a neurotoxin for olfactory neurons. Personally, all I can say is that if my ENT recommended a lemon-based, homeopathic nose wash I would find a different ENT. This sounds dangerous to me.


Why isn't smellovision a thing yet? Is there a limitation in technology or a lack of market interest?

Marshoon

There have been a number of attempts. John Waters used scratch and sniff cards (odorama) with his movie Polyester (early 80s, I believe). Go to Disney World and some of their shows have piped in odors. There have also been companies that have add-ons for your computer. In addition to creating realistic science (something at which flavor and gfragrance companies are getting remarkably good), there are also issues of odor removal, and of course cost. My guess is that this is going to be much more tractable when you are viewing a movie solo than in a big theater.


I have a really keen sense of smell. Almost like a dogs. My mother is the same. I can detect smells others can't and I am always the first to pick up on scents. I can small the slightest hint of rot in food when no one else can. Strong scents are irritating to me as I feel I perceive them stronger than others. Does this ability come with other superpowers I'm unaware of?

nomosnow

Not that I know of, but have you tried invisibility.

Much remains unknown about the mechanisms of smell loss...even less is known about what one could term hyper-osmia. My guess would be that you and your mother are just at one extreme of the normal distribution of human olfactory ability. But it would be informative to know why.


It would be interesting to know how well my senses of smell and taste are working. Is there a good way to find out? I live in France, so this is of course vitally important socially.

CypripediumCalceolus

Olfactory and taste testing need not be hard, but there aren't many easy options where you place your olfactory and gustatory ability relative to the broader population. In most cases, smell and taste testing is only done when there is suspicion of a problem. You may be able to find a scientific study that would enroll you. In France, you might want to inquire at the Center for Taste and Feeding Behavior in Dijon (https://www2.dijon.inra.fr/csga/index_eng.php ).


Hello Professor Munger,

Thank you for doing this AMA. I am a medicinal synthetic organic chemist and was wonder if you might comment on Terpenes and Terpeniods relative to smell and phenomenal reactions in animals. Plants use these compounds in amazing ways as deterring "bad" insects and invite "good" insects to visit their flowers.

Thanks for your time.

...create a great day...

Althekemist

There is a wealth of chemical signaling between animals, and between plants and animals. You are quite right that terpenes and related compounds play an important role in communication between plants and insects. But we wouldn't call them pheromones. Rather, "semiochemical" is the broader term describing a chemical used for communication between two organisms (side note...an aspect of my own research has long been focused on semiochemicals). The basic classes are:

Pheromone: a chemical released by one member of a species that impacts the behavior or physiology of another member of a species. Example: odors that induce reproductive behaviors.

Kairomone: released by one individual (emitter) and detected by another (recipient), it has a beneficial effect for the recipient. Example: a predator odor that induces a defensive behavior in the potential prey.

Allomone: released by one individual (emitter) and detected by another (recipient), it has a beneficial effect for the donor. Examples: substances released by plants that deter herbivorous insects that typically would eat that plant, or chemicals that attract pollinators.

In the examples you give, the terpenes are functioning as allomones.


I am curious about two things.

One - why do pregnant women have such a heightened sense of smell.

Two - why is my sense of smell when my sinus allergies are acting up?

Thank you.

mostpeculiar13

1) Changes in olfactory function in pregnant women has long been noted, but I am not aware of any study demonstrating a mechanism.

2) I think you missed a word in this second question, but allergies can definitely impact smell function. This may be due to the production of excess mucus or to inflammation.

You are welcome.


Why can we eat until we're full, then suddenly smell something else appetizing, and then be hungry again?

Quietwyatt211

Perhaps not surprisingly, our brain often has to deal with conflicting signals. Our digestive system can be sending us clear signals to stop eating while our olfactory and taste systems (and the pleasure centers in the brain with which they interact) may be telling us not to skip that piece of cake.

Perhaps this is an evolutionary remnant reflecting the fact that for most of human existence food was scarce and so you should not pass up an opportunity to eat when the opportunity presents itself. But whatever the explanation, I think it is a feeling most of us have experienced.


Why do some people have weird stinky feet fetishes, while others are repulsed by feet?

RetardsAdvocate

I have no idea, though you could probably pose the same question regarding any fetish.


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