Hyperosmia – The Superhuman Ability To Detect Scents

Hyperosmia is a heightened sense of smell, in which everyday odors seem far stronger than they do to most people. It is usually triggered by another condition, such as pregnancy, migraine, Addison's disease, Lyme disease, or certain medications, and it can cause nausea, headaches, and anxiety. There is no specific cure, so treatment targets the underlying cause.

Hyperosmia is a medical condition in which a person has a greater than average ability to perceive and sense odors. Hyperosmia isn't always a bonus to life. In fact, more often than not, it's actually a bane.
Castle Season 8 Episode 5 introduced us to Mia Laszlo. She was the prime witness to a murder, and a crucial part of the whole investigation, although she hadn’t seen the perpetrator’s face or heard his voice. She was portrayed as a funny, quaint little woman, and quite paranoid, who lived in an apartment where everything was clean and stink-free (OCD much?!) However, the reason she could help in the investigation was that she had smelled the killer. That’s correct. Smelled him distinctly enough to identify him. But is this even possible?

Mechanism Of Smelling

First, we need to understand how we smell. Our nostrils have a large number of nasal hairs that help filter the air. At the back of the nose, we have the olfactory epithelium. Olfactory is the technical term for smell, while the epithelium is the layer of tissue or skin that covers an organ. It has olfactory receptors covered by a mucous layer. Receptors are specific cells that receive signals. The receptors go up the nasal passage to a structure called the olfactory bulb, which leads to the brain.

The air contains a large number of odor molecules that are inhaled by us. These cannot just be inhaled; instead, they need to be carried to the back of our nostrils, to the olfactory epithelium. When these hit the back of the nose, they get stuck to the mucous layer and are dissolved. They then attach to the receptor cells. A biochemical reaction takes place and the signal is carried to the brain.

neuron Olfactory bulb olfactory epithelium nerve endings nasal cavity” class=”size-full wp-image-18940″ height=”513″ src=”https://uploads.scienceabc.com/2018/05/Bipolar-neuron-Olfactory-bulb-olfactory-epithelium-nerve-endings-nasal-cavity.webp” width=”576″/> Olfactory neurons. (Photo Credit : CNX OpenStax / Wikimedia Commons)

Each human nose holds millions of olfactory neurons, or receptor cells. Each neuron carries just one type of receptor, which responds to certain odorant molecules. There are only about 400 types of receptors in humans, yet there are roughly 6 to 10 million sensory neurons, so it stands to reason that many neurons share the same receptor type. But hang on! Humans can distinguish at least one trillion different odors, yet we have only around 400 types of receptors.

Confused? Well, each odor molecule can activate more than one type of receptor, and each receptor responds to more than one odor. Hence, even though we have just about 400 types of receptors, based on the combination of which types are activated, we can distinguish very specific smells. Think of it like a piano, as explained by Dr. Charles Wysocki. The keys are the different types of receptor molecules, your fingers are the odor molecules and the sound produced is the smell you finally detect. Depending on the combination of keys that you press, the sound you produce is different. So, although there are a set number of keys, the potential sounds produced are incredibly broad. 

Hyperosmia

Now let’s talk about the case of Mia Laszlo. During the process of smelling, at any stage from the generation of the signal until it is received by the brain, if the signal gets amplified, the sense of smell is heightened. Complicated? Let’s break it down. Consider an arbitrary scale of 1-10. When a person smells a flower, let’s assume the strength of the signal is 5. Now if the strength is amplified and becomes a 7, the smell would appear stronger to that person. This condition is called hyperosmia. Sounds pretty cool, doesn’t it?

This also allows the person to detect odors that a normal person would miss. How? While the exact reason is unknown, the general belief among researchers is that an odor may sometimes be too weak to actually generate an adequate response in a normal person. However, in case the signal gets amplified, it would become strong enough to be consciously detected by the person. This is supplemented by the fact that research has already proven that a person may sometimes not detect a smell consciously, but will still react to it subconsciously. 

Effects Of Hyperosmia

Before you wish this ability for yourself or anyone else, hold your horses. Hyperosmia isn’t always a bonus to life. In fact, more often than not, it’s actually a bane. Think about it. With this condition, every odor is heightened and amplified. Every. Single. Odor. The good, the bad and the terribly stinky! Most people experience nausea, gagging, and bouts of vomiting because they are unable to handle the various smells. Strong odors can also trigger headaches, and constantly bracing for the next unpleasant whiff can leave some people anxious or even depressed.

Picture something as simple as meeting a person. While a normal person may not perceive any stink, a person with hyperosmia will probably detect some sort of stink or bad odor, as every person has some amount of body odor. Due to this, many of these people are not very social. Sorry to burst your bubble, but things are not all that peachy. Yes, Mia Laszlo managed to help catch the killer because of his smell, but that woman lives in a house with a disinfecting chamber at the entrance! And she is HIGHLY antisocial.

Cause And Treatment Of Hyperosmia

Hyperosmia is genetically a rare condition. Very few people are born with it, but a person can also acquire it temporarily. Pregnancy is known to cause hyperosmia in many women. The degree of it may vary, but plenty of women report a marginally heightened sense of smell during their pregnancy. It goes away eventually, usually after delivery.

Another known cause is having a migraine. A lot of migraine sufferers also report a heightened sense of smell, and a systematic review found that close to half of them (roughly 25 to 50 percent, depending on when they were assessed) become hypersensitive to odors around their attacks. The reverse has also been seen, though, so there is no firm proof as of now as to whether hyperosmia triggers a migraine or vice versa. It can also be caused by exposure to toxic vapors or by certain underlying diseases. In certain instances, trauma to the nose can also result in hyperosmia. Although these factors can cause hyperosmia, they don’t always. In fact, most of the time they result in other olfactory conditions, such as a reduced ability to detect odors (hyposmia), or the loss of the ability to detect odors (anosmia).

A surprisingly long list of medical conditions can dial up the sense of smell too. Addison’s disease, an adrenal gland disorder, can make smell and taste so sharp that doctors have used the symptom as a clue to diagnose it. Lyme disease, which attacks the nervous system, can scramble smell as well, and so can autoimmune conditions like lupus. Several neurological diseases (including Parkinson’s, epilepsy, multiple sclerosis, and Alzheimer’s) are linked to altered smell, and certain prescription medications, drug withdrawal (such as from benzodiazepines), and a vitamin B-12 deficiency can do it as well. In other words, a sudden heightened sense of smell is often the body’s way of flagging that something else is going on.

There are very few treatment options available, and there is no specific cure, so the main aim is to treat whatever is causing it. Most of the time the condition simply goes away on its own, as it does when it’s brought on by pregnancy or a migraine. Doctors usually start by adjusting any medication that might be the trigger and recommending that the person avoid strong-smelling spaces. In some cases of hyperosmia caused by disease or trauma, corticosteroids or even surgical procedures may help. If the condition is genetic, it is usually not treatable.

Keep in mind, however, that due to its rarity, the mystery of hyperosmia hasn’t fully been unraveled yet. Even now, very little is known about the condition. And while it may seem really nice on screen, it’s best to leave it there.

Why Does My Sense Of Smell Suddenly Feel Stronger?

One of the most common questions people ask is why their nose seems to switch into overdrive out of nowhere. The reassuring answer is that a sudden jump in smell sensitivity is usually temporary and tied to some passing change in the body, rather than a permanent rewiring of your sense of smell.

Pregnancy is the classic trigger. Around two-thirds of pregnant women rate their sense of smell as stronger than normal, and it tends to be most noticeable in the early weeks, especially during a first pregnancy. Here is the twist, though. When researchers actually test the nose in a lab, they generally find no real increase in the ability to detect faint odors. What changes is how smells are judged. Expectant mothers tend to rate many odors, particularly food and unpleasant ones, as far less pleasant than before. In other words, the nose isn't necessarily sharper, but the brain's reaction to smells shifts.

This is exactly why does a strong sense of smell mean I'm pregnant? is such a popular search. The honest answer is no, at least not on its own. A heightened sense of smell is not a reliable pregnancy sign, and plenty of people notice it without being pregnant at all. Other temporary culprits include a migraine building up or certain medications. If the change appears suddenly and settles over days or weeks, it is usually nothing to worry about. If it lingers, it is worth asking a doctor to check for an underlying cause.

Why Do Strong Smells Make You Feel Sick?

If a whiff of perfume or frying oil can turn your stomach, you are not imagining it, and there is even a name for it. That aversion is called osmophobia, a strong discomfort or dislike of odors. It is worth separating from hyperosmia. Hyperosmia is about detecting smells more strongly, while osmophobia is about smells making you feel awful.

Osmophobia shows up most often alongside migraine. A recent systematic review and meta-analysis that pooled 58 studies and more than 22,000 patients found that close to half of people with migraine (about 48 percent) experience it, and those who did were significantly more likely to also feel nauseous.

So why does a smell reach all the way to your gut? The trigeminal nerve, which carries sensation from your face and the lining of your nose, plugs straight into the brain's pain circuits. Irritant odor molecules can switch on sensory receptors in the nose (a channel called TRPA1), which releases a messenger called CGRP and fires up the same trigeminal system involved in migraine pain. Here is the surprising part. People with migraine and osmophobia don't necessarily have a keener nose. On standardized smell tests they often score no better than everyone else, and some are actually worse at identifying odors. It is the brain's reaction to the smell, not the nose itself, that has been turned up.

Is A Heightened Sense Of Smell A Sign Of Cancer?

This worry sends a lot of people to the internet, so let's clear it up. A heightened sense of smell on its own is rarely a sign of anything sinister, and it is almost never a signal of cancer.

Part of the confusion comes from mixing up two different experiences. Hyperosmia means real smells seem stronger than they should. Phantosmia is different. It is smelling something that isn't actually there, a phantom odor such as smoke or burnt toast that no one else can detect. The cancer fear usually attaches to phantom smells, not to a generally sharp nose. Even then, specialists at MD Anderson Cancer Center point out that phantosmia is far more often caused by something harmless, such as a viral infection like a bad cold or COVID-19, a migraine, a neurological condition such as multiple sclerosis, a seizure disorder like epilepsy, or a head injury, than by a brain tumor, which is a rare cause. Phantom smells are also usually temporary, even after a nasty infection.

None of this means you should ignore a change that won't quit. If a phantom smell or an unexplained shift in your sense of smell lasts beyond two to three weeks, it is worth seeing an ear, nose and throat specialist, who can look inside the nose and arrange scans if needed.