I think I am a super smeller, and here’s how the world smells to me

The pop star Lorde can identify an imitation of Santal, a fragrance from New York perfume brand Le Labo. So can I. Reading her profile in The Good Weekend, I felt a kind of kinship with the artist.  She says if she ever made a perfume, “it would be the fragrance of crushed tomato leaf. Everything’s got a smell to me.”

I feel pretty much the same about smells. My heightened sense of smell as a child often got me in trouble because I would reject some foods if they smelled a particular way.

As I grew older that strong sense of smell transcended to cancelling my physics tutorials as my tutor seemed to have an unpleasant body odour and socks that didn’t seem to have been washed for months. As he would explain the principles of electromagnetism my brain would be fighting the nausea initiated by the smells and I would constantly look at the clock.

Eventually I had to tell my parents that I wasn’t able to grasp much from his tutoring. 

During religious functions at a relative’s house, I would stop-start my breathing if the incense they burnt was too strong for my sensitive nose.

Lorde and I  both may  belong to a category of people called super smellers. Medically known as hyperosmia (osmia meaning sense of smell), being a super smeller  is a rare condition defined by having a  heightened sense of pleasant or unpleasant smells.

The small number of studies carried out on hyperosmia prove that the condition has a medical reason or could be a part of a syndrome. Some women report transient hyperosmia during pregnancy. In essence, people can either be born with a heightened sense of smell, or they can train themselves to have increased sensitivity towards certain smells, like sommeliers with wine or perfumers with fragrance.

But even with this understanding, our sense of smell is the most underrated and under researched sense when compared to the other four senses.

Hyperosmia: A Blessing or Curse

For me, the realisation that I had a heightened sense of smell didn’t come until much later. As a child, I remember walking into the house from the school and telling my mum what curry she had made much to her surprise.

I always assumed that everyone could smell to the same strength as me. A few years ago in my working life as a surgeon, I remember telling my anaesthetist that I could smell anaesthetic  gas (sevoflurane) and asked if there was a leak in the tube placed in my anaesthetised patient’s mouth. Sevoflurane is a bitter smelling anaesthetic agent that is used to put people to sleep. 

The assistants who scrubbed-in with me could not smell the gas through their masks but the anaesthetist knew that my sense of smell was a bit of a pain from previous experiences, and he decided to check the fit of the tube. No surprise, he agreed there was a leak and that the tube needed to be adjusted to seal it. Now he always jokes that he’d trust my nose before the machine. But, the flip side of such a sensitive nose is that  I can get affected by inhaling very small quantities of  that gas over a long session. 

My heightened sense of smell is a blessing and a curse. I cannot withstand strong perfumes and they make me nauseous, which means I’ve  had to move positions on public transport because I couldn’t bear the perfume of a fellow traveller. But it also means I am likely to venture into a shop that smells of calming essential oils and will end up buying something that I don’t need. Plus, I have to chuck out things from the refrigerator in a pretty timely manner. Such is the power of l’odorat – the sense of smell.

The fascinating science of noses and smell

On an average there are 400 receptors that are capable of detecting about a trillion different smells. Compared to the other senses in the body such as sight – eyes have only two types of photoreceptors ,one for light and another for colour vision. For touch, our skin has three types of receptors - for touch, pain, and temperature. For taste, our tongue has five types of receptors - bitter, sweet, salty, sour and umami; and for hearing, our ears have one type of receptor -mechanoreceptors for  vibration.

The nose dominates the other sensory organs in the complexity of its receptors. And to further complicate the picture, the way the neurons or nerve cells are wired in the brain results in our sense of smell also altering our sense of taste. An area where this is well explored is wine tasting, where one is often advised to swirl the wine to bring out the aroma, smell it, and then taste the wine to make the  experience complete.

So what goes on behind the scene? Olfaction, or the process of smelling, begins when any odorous substance enters the nasal cavity via inhalation through the nose or rising through the mouth from a food or beverage. These molecules bind to receptors that signal to the olfactory bulb, located in the pyriform fossa, a small cavity in the front of the skull bone. This activates a complex neurological transmission of signals responsible for smell recognition, memory, and emotion. 

The neurosensory pathways of olfaction (smell) also communicate to the other parts of the brain that regulate emotion. Hence, certain smells or odours evoke strong emotional reactions including nostalgia and longing.

Smell and nostalgia

The emotional connections to different smells can get amplified in super smellers. For example, petrichor, the smell of the first rain as it hits the earth after a very warm dry  weather, classically in mid-June in India, has a strong correlation with fritters or bhajiyas in my brain.

The wind on a hot summer day in Melbourne that is about to burst into a shower often cajoles me back to my childhood school summer holidays in India. I find myself breaking into a cooking spree, frying some onion bhajis on the other side of the globe.

But my sense of smell is relative. I’m not sure how sensitive my nose is to different ranges of odours. Quantifying that sense and depth of smell is hard according to some researchers.

Carl Philpott  a professor of rhinology and olfactology at the University of East Anglia in Norwich, UK conducted a study with 230 volunteers to test their depth of smell for the smell of the smell of roses (phenylethyl alcohol) or  a mint/eucalyptus-like smell (eucalyptol)). The depth of smell relates to how small a concentration of an odour can be detected – known as the “threshold”.

He found that two per cent of the group demonstrated “the superosmic phenomenon,” the technical term for super smelling, on single testing. A further 10% demonstrated this phenomenon on various occasions during repeated testing.

Professor Philpott says that super smellers are a mixture of people who may be genetically wired to smell better, some who train to smell better, and some who have an underlying medical condition. And others, perhaps including pregnant women, may only experience smell sensitivity – not true hyperosmia. 

Regaining the ability to smell

Losing our sense of smell and taste are now well-accepted early signs of coronavirus infection. 

To help people  who are affected by Covid-19 and have not fully recovered their sense of smell, or suffer from what is known as parosmia or post-viral olfactory dysfunction smell training is being developed by researchers.

Recently, a team led by Sandeep Robert Datta, a neurobiologist at Harvard Medical School in Boston, Massachusetts, has found that coronavirus affects the cells that support sensory neurons in the nose — known as sustentacular cells. But luckily the virus does not reach the part of brain that deals with olfaction or smell. That means after experiencing COVID illness,  there are  low chances of a permanent effect on a person’s sense of smell.

While early studies report that most patients have recovered their sense of smell eventually, there is a small group of people who haven’t recovered their sense of smell or taste. And for some, pleasant odours are warped or altered.

The Dutch Clinical Olfactory Working Group, or the Dutch smell-scientists team, has published a consensus statement for treating problems related to the sense of smell (post-infectious olfactory dysfunction). Mainly, the trial treatments focus on smell or olfactory training using natural substances. 

When we can’t smell

Some people argue that if we were forced to let go of one of the five senses, the sense of smell would top that chart. But there are serious dangers to not being able to smell. 

The loss of our sense of smell has real consequences. A 2014 study found that people with smell loss, or anosmia, were more than twice as likely to experience a hazardous event, such as eating spoilt food, as people without smell loss.

People whose sense of smell is impaired are unable to distinguish toxic substances, spoiled food or smoke. They may also miss out on bonding with a loved one such as a new-born baby that often evolves a multi-sensory experience including the much cherished “baby smell.”

I cannot imagine a life without being able to smell things as I do. And while I don’t think I could come up with an original perfume smell based on a crushed tomato leaf like Lorde, the super smeller in me will continue to alert my anaesthetist and make onion fritters every now and then.

Dr Krati Garg is an oral surgeon and a writer.